DISCLAIMER: I do not own Kimetsu no Yaiba or NieR. Both are properties of Koyoharu Gotōge and Yoko Taro respectively.

I do not own the cover art. All credits go to Deviant Artist dishwasher 1910.

2B(a)DEMON SLAYER

CHAPTER_02: Sun And Moon Will Forever Be Intertwined

Ten Years Later...

15-year-old Tanjiro Kamado had arrived at Fujikasade Mountain with anxiety and nervousness bundled together. Each of his footsteps was shaky, but not out of fear. Instead, he was dreading what he was to face. Having lost his whole family to a demon, and his sister turned into one herself, he had truly gone through hell. He had trained for two years in order to become a demon slayer in the hopes that his adventures would lead him to finding the means in which he could return her to normal. However, choosing this path meant risking his own life. A sacrifice he was more than willing to undertake if it meant he could restore Nezuko to normal.

As for why he arrived at Fujikasade, it was because the exam in which he may or may not become a demon slayer was taking place here. The Final Selection. His teacher had been pretty tight lipped about the whole exam, but what he did tell Tanjiro was that demons would be involved, hence why he was given a sword capable of killing a demon. If he succeeded in passing the exam, he would be given his own sword and uniform. That said, he couldn't afford to be careless even if the demons on the mountain were thought to be incredibly weak, having been starved and trapped.

The reason why they couldn't leave just happened to be the flowers that were dangling from tree branches, creating a beautiful purple florescent glow that captivated him as he passed under them, their scent sweet and soothing. The wisteria was a flower that was apparently both toxic and dangerous towards demons, enough so that they were repulsed by the smell. If they ate it, they'd be suffering from poisoning.

Every weakness and advantage demons had was pounded into his head, as were the sword techniques his teacher passed on to him in the two years he had been under his care. Now it was time to put that knowledge to the test.

After a minute or so of walking, Tanjiro arrived and stopped. Dozens of people, all carrying weapons similar to the one at his hip, were gathered in one place, each either confidant, terrified or anxious or all three at once. In particular was a boy with an ugly scar, his eyes scarily intense and fingers twitching. Another boy, hair blonde, looked scared out of his wits. Another was eerily calm, expression serene.

But the one who captivated him the most was the one who stood off to the side, wielding not one but two swords. One was fastened on her back while the second sat at her hip. She wore a black sleeveless kimono with a white sash around the waist, pouches dangling from the belt. She wore wooden sandals and knee-high black socks, a black hairband atop her snow-white hair. Oddly, the upper-half of her face was blindfolded, perhaps implying that she had been scarred.

Everyone present had a unique smell. The boy with the scar smelled like blood, but not like the demons. The terrified boy smelled like thunder clouds, and the serene girl smelled like wisteria. The blindfolded girl, though, had a more unique smell to her.

If he were to describe it, he thought she smelled like the moon...if that made any sense. There was no other way he could put it into words.

"Are they all here for the Final Selection...?"

He realized that many would be part of the Final Selection to become Demon Slayers. But he never would've thought he would run into people like them. Their scents were just so unique. It was unlike anything he's experienced before.

Although, his thoughts were focused on the moon-scented girl. Unlike everyone else, she carried two swords, one of them in a unique manner. Perhaps she was capable of dual wielding?

"Welcome."

Tanjiro was pulled from his musings, now taking notice of the two little girls that stood at the head of the crowd of people. Twins, both dressed in purple yukata with floral designs. While both had dark purple eyes, their hair color differed. One had black hair and the other had snow-white.

'Who are they?' Tanjiro wondered curiously. They seemed awfully young to be attending the Final Selection. Actually, they couldn't be more than seven or eight.

"Everyone has been gathered." the girl with the black hair spoke. "Thank you all for attending this year's Final Selection. Fujikada mountain is home to many demons that have been captured."

"They cannot leave this mountain, as the wisteria here blooms at the foot of the mountain all year round." the girl with the white hair continued.

"However, there will no longer be anymore wisteria from this point forward. In other words, for the rest of your stay here, you will face the demons trapped here."

"Your task is to survive for seven days, and kill any demons you may encounter. Those who survive those seven days will have succeeded in completing the Final Selection."

The twins bowed and stepped aside, speaking in unison. "Let the Final Selection begin."

Those words set them off. Everyone rushed past them, either eager to find a hiding place and others looking forward to have their steel taste demon flesh and blood. Tanjiro was the last to follow them, trailing behind the rapidly dispersing group while keeping his nose sharp for any unusual smell. In his heart, he was hoping that there might be a demon here that could help give him the answers he was seeking. Surely, at least one of the demons here must know something about returning Nezuko to normal. And if not them, then maybe...

"Listen, Tanjiro. In the past 400 years, there has only been one demon that is capable of creating other demons. The first demon, and the mortal enemy of all demon slayers. The name of that demon is...Kibutsuji Muzan."

Muzan. The name of the first demon. The bastard who killed his family and turned Nezuko into a demon.

He gripped the hilt of his sword tightly, eyes burning and heart ablaze.

Two days passed. Two days with barely any rest or sleep. The mist in the air was thin, but the danger it represented did not lessen just because of that. She kept her wits sharp and her blade at the ready, ears listening for the faintest movement while her eyes looked past the cloth that bound them. To some, it looked like she was wearing a blindfold. In a way, they would be correct. The blindfold had no functions beside hiding her sight from her, but it served a purpose. Using one's eyes was not always the only way to determine where a potential threat may come. And while her eyes may be obstructed, that didn't mean she could not see what was in front of her. Her ears did not pick up the faintest sounds like echolocation and create a "map" of her surroundings.

Instead, she had used what Isshin had taught her. To see the world as it must be seen.

"Your eyes betray you." Isshin told her. "They betray the world, too. What you see on the surface is how the world should look, but it is now how it actually should. Do not let your sight show you what is and is not in front of you. Instead, use the eyes in your mind."

And so, she did. And when her hidden eyes opened, her sword was drawn.

"Tsuki no Kokyū, Ichi no kata: Yamizuki - Yoi no Miya."

Her swing was a blur. From a single stroke came a myriad of smaller, crescent slashes that shredded the approaching demon within range. The twisted soul had no time to realize it was dead until it's head was severed while its body was minced to pieces.

As its body began to break apart into ashes, 2B slid the blade back into its sheathe. The katana fell inside with a 'click.' With another demon slain, she continued her assigned task. In the short time that passed, she encountered only two or three others who stubbornly chose to fight by themselves instead of finding a group. The odds of survival were much higher if people trusted one another to survive, especially in the present circumstances.

Still, she doubted they would have much trouble unless they got cocky. Compared to the demons Isshin threw her against in Shanghai, the ones trapped here on the mountain were pitifully weak. That was to be expected, given they were starved and have only eaten a small number of people - the fates of other individuals who took the test and died at their hands notwithstanding.

And yet, she could see it. A pungent, almost violent air that burned. Somewhere within the bloody mist her eyes could perceive, a portion of it was thick.

There was a powerful demon lurking here in the mountain. Possibly having devoured many demon slayers, and perhaps even members of its own kind. Her uncle did mention to her that there were recorded cases of demons committing cannibalism, though they were quite rare. As to why a demon would eat another demon, the theory was that the demon committing cannibalism would grow stronger by feasting upon the flesh of another demon and undergo a mutation. Even develop a Blood Art they never had previously. Of course, there were no cases of there being demons with two Blood Arts, so it was more likely that the cannibal developed a Blood Art of their own, or perhaps took it from its victim.

At any rate, 2B's goal was to survive for seven days and kill any demon who got in her way. There was no reason for her to kill something that could prove potentially dangerous. She could not afford to take any risks.

However, if the demon was threatening another one of the humans here, then she would intervene. To defend humanity was her task, after all.

As she continued on her way, moving up closer towards the base of the mountain, she suddenly stopped when she saw the mist shift subtly. Another demon was approaching. Her thumb pressed up against the hilt of her katana, ready to slay it the second it emerged. She waited patiently, foot rooted to the ground while keeping her body tense. Her breathing changed, smooth and calm while her body grew tense.

Twelve seconds passed before the demon emerged. Just as she was about to strike it in a single blow, something bizarre happened.

Namely, the sight of what looked like a man with a boar's head headbutting the demon straight into its abdomen and sending it flying.

"Gyahahahahahaha! Pig Assault! Pig Assault! Gyahahahah!"

2B's eyes blinked underneath the blindfold. The head of a boar was a mask as she did not see the lips move at all. The fur was also wrong, hairs too thick and the eyes not made of thin membrane and flesh. The man's body was muscular and well-toned, implying good physical training. His stance was completely full of holes, but the way he gripped his swords showed that he was no stranger to combat. The mist surrounding his body was brown and wild, akin to a beast ready for battle.

Before 2B could properly assess what was happening, the pig-masked man let out another battle cry and charged after the demon who realized it was in danger and fled. She watched the two vanish further into the forest, too dumbfounded to chase after them.

Instead, she could only make an observation. "The humans of the Taishō period are strange indeed."

On the third day, Tanjiro encountered both a great danger and his first real test as an up-and-coming demon slayer. He had finished slaying two demons and offered his respects, hoping they would be find a happy life in the next world when he felt a disgusting smell suddenly invade his nostrils. Not a second later, a shrill scream pierced the air and alerted him of the presence of yet another demon, chasing after one of the applicants of the Final Selection.

The source behind the nauseating smell was perhaps the most warped demon he saw. He couldn't make an actual body, for every inch of it was covered in thick burly arms. The only visible portion of its body that he could see was its head, which was also wrapped in arms and bearing golden eyes with cross-shaped slits. Its skin was dark green, veins throbbing underneath its flesh.

Worst of all was the thick sent of blood. Tanjiro couldn't help but tremble.

'How many people has this monster eaten?!'

"D-dammit!" the demon's target cursed as he scrambled to escape. "W-why is there a mutant type here?! We weren't told about this!"

The demon let out a low chuckle before it raised what Tanjiro assumed was its actual left arm. It extended and reached out, grabbing the applicant by its angle. The red-haired boy didn't need anymore time to think and let his body move on its own. He sucked in a breath and felt his blood explode in his veins, muscles becoming thick.

"Mizu no Kokyū, Ni no Kata: Mizu Guruma!"

His body spun forward while the blade carved through the air seamlessly as if it as treading through water. He sliced straight through the appendage easily. The grip slackened and the applicant was released, dropping to the ground with a yelp. The demon was surprised by Tanjiro's sudden appearance, but didn't seem too angry or shocked by the loss of its limb.

Immediately afterwards, Tanjiro put himself between the applicant and the demon, sword raised. 'This one is completely out of my league. There's no way I can take it on without risking serious injury. Even so, if I can just buy him enough time to escape, then...!'

"...kekekekeke. I've found another fox." Tanjiro blinked when he saw the demon laugh. For some reason, its eyes fell on the mask his teacher, Urokodaki, had given him when he set off for the Final Selection. "Tell me, fox... What year is it now?"

Tanjiro was surprised a Demon would ask such a question. But he steeled himself and responded. "It's the Taishō Period now!"

"Taishō...?" The Demon rolled its eyes in contemplation. After a few moment, its eyes snapped open as it roared. Its body thrashed around, its multiple arms flailing about, some of them clawing deep into its own flesh. Tanjiro and the boy he saved could only look on in morbid fascination. "Holy shit! Time has passed into a new period?! Again! Again while I've been held prisoner in this wretched place?!" His arms trembled as if they could shoot out at any time. "Damn you, Urokodaki! Damn you Urokodaki!"

Tanjiro's eyes widened. "Y-you know Urokodaki-sensei?!"

"Know him?! Of course I know that bastard!" the demon snarled, eyes full of hate. "He's the bastard who threw me onto this mountain! I could never forget that bastard! I remember him well, ever since the day we met 47 years ago during the Keio Era!"

The red-haired boy choked. The boy behind him stared in shock. "That can't be right! There are no demons who've lived for that long here on this mountain! If there were, they'd have been killed either by themselves or by other Demon Slayers! That can't be true!"

The demon laughed, its hate for Urokodaki now forgotten. "Oh, but I am here. I've been on this mountain for four decades now." His eyes once again fell on Tanjiro, or more specifically the fox mask he was wearing. "I've devoured fifty humans in the time I've been trapped in this god-forsaken place." Tanjiro froze. He remembered Urokodaki's lecture about how powerful demons could become based on the number of humans they devoured. It certainly explained the horrid smell. And more importantly, the threat that was standing in front of him. "Let's see... Twelve, thirteen, and the last one was... Yes, you little boy. You'll be the fourteenth fox I will have eaten."

"Fourteenth?" Tanjiro narrowed his eyes. "What do you mean?"

"You got that mask from Urokodaki, riiight?" the demon pointed to the item in question. "I remembered the first person I ate who wore that mask as he cried for Urokodaki's forgiveness for failing some kind of test. Then came another little fox I found, who muttered those same words. That's when I realized anyone who was wearing fox masks were all of Urokodaki's cute little students." Though Tanjiro couldn't see it beneath those arms, he was certain the demon was smiling wickedly. "And I've made sure to eat all of the cute little foxes who've crossed my path. I remember some of the more important ones, like that strong kid with the scar or that little girl that tagged along with him."

His blood went cold. His heart dropped. The description it just gave, he knew immediately who he was talking about. His other teachers, besides Urokodaki. The two who helped him cut straight through that boulder with all of his might.

Sabito and Makomo. Two others who wore the same fox mask he did.

"I made sure to remember the distinct designs of the mask, so I knew which ones were Urokodaki's students. I think one of them called it a mask that prevents disaster, right? It's a shame that all it did was lead them to their deaths." The demon laughed once more, this time full of bitter anger. "It's almost like Urokodaki sent them to their deaths. Oh, I wish you could have been there. That little girl with that strong boy got so angry she tried to kill me, but her movements became so rigid. She made it so easy for me to tear off her arms and legs. Kekekekekeke!"

Though he was usually as calm as the ocean waves, something about the way the demon gloated about killing Makomo caused something in him to snap. A burning scream ripped from his throat as he charged straight at the demon wick reckless abandon. In response, the demon shot several arms straight at him. Each arm was severed with ease, but Tanjiro's breathing became erratic. The strength in his body slowly began to dip.

"Calm yourself, Tanjiro." a familiar voice whispered in his ear, but couldn't break through the haze of hate that was clouding Tanjiro's mind. "Your breathing is all over the place. Stop thinking about what happened to us!"

Tanjiro couldn't hear those words in time, for in his recklessness he was punished as two fists suddenly crashed straight into his ribs. He felt bones crack from the impact and the wind knocked from his sails before he was sent flying, landing face-first into the ground. He rolled away from the demon until he came to a stop, his mind left in a daze. The whole world was spinning. His stomach was lurching uncomfortably, and his side was flaring in pain. He knew for certain that his ribs were cracked, but he couldn't afford to let it cloud his mind. He had made a mistake, and now he was paying for it.

Even so, he had to fight.

With a wicked laugh, eager to see yet another student of Urokodaki dead and in his belly, the demon sent out another wave of arms towards Tanjiro. Still dazed and recovering, he had little to no time at all to defend himself, much raise his sword.

At that moment, however, someone intervened as a familiar scent, akin to moon-filled night, entered his nostrils.

"Tsuki no Kokyū, Hachi no Kata: Getsuryū Rinbi."

A sword cut through the air, but the blade itself never touched the demon's arms. Instead, a crescent wave made entirely of air did the dirty work and easily sliced through the arms.

"What the hell?!"

Tanjiro was just as surprised. What was that technique? Who did that?

"Calm yourself." a soothing voice admonished him. The scarred boy blinked. Standing between him and the Demon was the blindfolded girl he saw at the entrance. "Your breathing is erratic. Take a moment to calm down. You can't fight if your breath is uneven."

Tanjiro stared at her for a moment, then nodded. "R-right. Thank you."

2B froze. The second the boy with the crimson aura spoke, his face overlapped with someone else's.

This moment, it reminded her of something. No, it reminded her of someone. Their facial features were a little similar, and their voices were the same, but whereas the scarred boy had a tone of innocence and gentleness, 9S was curious with a hidden biting edge to it. They were two different people, much less two different beings. One was human, and the other was an android.

She took a quick breath to calm herself down and remove such unnecessary thoughts, instead focusing on the demon in front of her. She had hoped she didn't need to get involved, but she saw someone running away from the same direction where the intense portion of the mist emanated, where it was quickly overwhelming the mist that surrounded the scarred boy. The mist surrounding him was odd, dyed the color of pure flame but danced around him like waves in the ocean.

At any rate, 2B found herself engaging the demon. True to her expectations, its form was radically different from the ones she encountered previously, though based on what she just saw it didn't appear to possess any form of Blood Art. How many demons and humans must it have devoured in order to obtain such an appearance, much less developed such grotesque abilities?

She looked at the stumps of the arms she severed, only to find that they had already regenerated. Its regenerative ability was amazing. It took maybe four or five seconds for it to repair the damage it sustained.

That would make killing it difficult. Of course, there was a more effective way to kill the demon. That was, naturally, to sever its head from its neck. Getting up close, however, would be difficult. Its raw strength and ability to regenerate, much less its multitude of hands, would make it difficult for them to get in close enough to deliver the killing blow, as well as escape.

"Can you still fight?" 2B asked the scarred boy.

He nodded. "Y-yes, though I think that last attack cracked a few of my ribs."

"Power through it. Get ready." She drew her sword from its sheathe. "He's coming."

"You damn bitch!" The Demon snarled at 2B, his hands twitching madly. "That fucking hurt! I'll kill you! I'll rip off all your limbs and eat them one by one!"

2B only looked at the demon for a moment before she and the scarred boy both moved forward. At that moment, the demon sent out several arms to intercept them. With fluid movements akin to a water stream, the scarred boy cut through each arm. His advance was halted much like herself, though in contrast to his fluid movements she moved much faster. Though she was still nowhere close to the level she was at in her previous life, she was still fast on her feet and just as capable with her sword. However, she could not withdrew her other blade.

Not yet.

'Keheheheheh. That's it, just focus on what's in front of you!' the demon thought with a sneer as one of its arms burrowed its way underground, slithering towards its target. 'Even if you two fight together, I've already won!'

The scarred boy spun in a full circle, slicing off several arms before he stopped. He glanced at the ground, nose twitching, then leaped off the ground. Just in time, as he evaded an arm that exploded from up out of the ground, fingers open with the intent of breaking all of his bones at once the second he was in his grasp. 2B clicked her tongue as she spun on her heel, dismembering the limb before performing two backflips, evading two more arms and chopping them off in the process.

The demon was stunned by the scarred boy's ability. To think he'd sense his arm coming up from below to grab him! But that surprise gave way to glee, for even if he could evade that attack, there was no way he could defend himself in mid-air. He capitalized on the young boy's foolishness and sent an arm forward, intent on breaking his neck. The boy glared as he reared his back, and to the shock of both present, rammed his forehead straight into the incoming fist. Even more shocking was that the force behind the headbutt was enough to divert the arm's direction.

'He diverted that attack with a headbutt?!' 2B stared in shock. 'How thick is his skull for him to accomplish that and not become disoriented?!'

Taking advantage of the momentum created by his headbutt, the scarred boy landed on the demon's arm and charged, blade poised to sever its head. The demon, in one last act of desperation, sent several arms towards him. 2B would not allow that to happen, not even for a moment. She sucked in a breath and let it spread through her body. She launched herself forward, her empty hand reaching for the blade on her back. The sole memento she had of her father and her grandfather.

"Tsuki no Kokyū, San no Kata-"

The blade was withdrawn from its sheathe. Twin swords in hand, 2B let them roar with all their might. For a brief moment, the light of a full moon reflected on the blades. The demon saw this and, for a brief moment, saw a terrifying figure behind her. The man who was with the same person who made it. Though he was but an image, faint and hallucinate, there was no stopping the terror that echoed throughout its very being as six hellish eyes glared down at it.

"-Enkizuki - Tsugari!"

The blades were swung and created twin razor-sharp arcs of wind that flew straight at its arms. However, in mid-flight smaller crescent arcs formed around them and scattered. Within seconds, the demon's last ditch effort to kill Urokodaki's student were chopped to pieces. Some of the arcs even sliced away at his own body, creating small but deep cuts.

'N-no way... She destroyed all my arms in seconds. Shit. I can't regenerate my arms in time.' The scarred boy drew closer, his blade ready to deliver the killing blow. 'But, even if I die, I can still take this kid with me. Not even that kid with the scar could cut through my neck. Once he fails, I'll have just enough time to kill in and crush his head in!'

And yet, despite those words, the demon could only feel unadulterated fear as the boy neared. Just like before, when 2B had cut apart his arms, he saw an image overlap with his quarry. Instead of a boy with fiery red hair and a scar, all he saw was that dreadful visage of a man leaping at him, blade raised and Tengu mask shielding his face.

"Uro...kodaki...!"

"Mizu no Kokyū, Ichi no Kata: Minamo Giri!"

Streams of water flowed across the blade as Tanjiro swung horizontally. Blade met reinforced neck.

Blade emerged victorious. The forged edge cleaved through the Demon's neck like a hot knife through butter. The Demon did not realize his demise until he blinked. Once. Twice. His view of the world tumbled and turned as he saw his body collapse right next to him. 2B let out a sigh as she slid her swords back into their respective sheathes. Similarly, the boy had done the same. Even so, the former did not relax. They couldn't afford to just yet. For all they knew, the demon must still have some tricks up their sleeve. Not even the lessening of the bloody mist around the dying mist made her relax. She looked at the demon's corpse as its body gradually began to break down into ash. Looking at its head, she saw that its golden eyes were locked on to the scarred boy, glaring at him with hate. Not that she would have expected anything less from such a miserable and despicable creature.

She looked at the scarred boy, intent on asking him if he was alright, when she saw the look in his eyes as he turned to look back at the demon. Instead of arrogance over having prevailed, smugness for having defeated an opponent stronger than he, relief that he had survived, she instead only found sadness and pity. Both emotions were directed at the demon's decaying head. But that didn't make any sense to her. Why would he feel pity for a demon? The demon itself seemed to share in her feelings, as its hate was discarded and just stared at the boy, unsure of what to make of him.

A motion caught her attention. The body moved, but only slightly. It was obvious the demon no longer had any strength left to enact a final attack. All it managed to do was open up its hand. The scarred boy looked back at it, then glanced once more at the decapitated head before he did something that confused her even more. He wrapped his hands around the demon's own hand.

"Kami-sama, please. Never let this person become a demon again when he reincarnates..."

The demon stared at him, eyes wide as tears spilled down its face. That was the last look it had before its head, as well as the rest of its body, fell apart into ashes. The boy looked down sadly at the pile of remains, still looking pitifully at it. 2B did not understand why he was doing that. Why was he pitying that monster?

"Why did you do that?" she found herself asking. "Surely, you must have known. That demon devoured many people. It did not deserve kindness."

The boy looked at her with a sad smile. His answer surprised her. "...because even he was a monster, he was human once."

2B stared at him for a moment, then shook her head. He looked to be fine in spite of his injuries. Surely by now, the number of demons on the mountain must have thinned. And with such a threat now eliminated, there would be less risks involved. She turned on her heel and left, feeling his eyes on her back.

She sighed. "Even after all this time, I still do not understand humans."

Four days went by after that fateful encounter. The sun had already begun to set when Tanjiro had reached the base of the mountain. When he was greeted with all the others who had survived the Final Selection, he couldn't help but look in shock.

"O-only five?!"

The serene-looking girl, the blonde boy, the boy with the ugly scar, the girl with the blindfold and himself. That was all that stood before the twins. Compared to the dozens of people who were here previously, he couldn't help but feel dismayed. How could this be possible? Surely, more must have passed. Maybe some just didn't make the cut and realized they were in over their heads or something? Or what if they had...

His mind drifted back to the third day, when he saved an applicant from the demon who killed Urokodaki's students and his predecessors. Had that person not survived after all?

His heart ached. He bit his lip, fingers digging into his palms. This was not fair whatsoever. Why had only the five here managed to survive? There must have been stronger people among them, right?

"Welcome back." the girl with white hair greeted as she and her sister bowed.

"You have returned, alive and well. Congratulations."

"What do we do now?" the boy with the scar asked rather rudely. "What about our swords?"

His question went ignored. "First, you must pay the cost of your uniform, then have your measurements taken."

"Afterwards, your rank will be engraved in your uniform. There are ten ranks."

"Mizunoto. Mizunoe. Kanoto. Kanoe. Tsuchinoto. Tsuchinoe. Hinoto. Hinoe. Kinoto. Kinoe. Currently, you are all Mizunoto, the lowest rank."

"What about our swords?" the boy with the scar asked again, this time sounding more annoyed than anything.

"You will choose a piece of Tamahagane Ore." the girl with white hair turned to him. "The sword will be completed within ten to fifteen days. Additionally, you will be accompanied by a Kasugaigarasu from today forward."

She clapped her hands. To Tanjiro's surprise, four crows and a sparrow emerged from the trees, flocking to their side. One perched itself atop his shoulder and let out a squawk of pride. The blonde-haired boy stared at the sparrow in confusion while glancing at the rest of the crows, wondering if there must have been some kind of mistake. The boy with the scar, however, smacked his crow away when it attempted to perch itself to his shoulder.

"I don't care about a stupid crow!" He stomped up to the girl with the white hair and grabbed a fistful of her hair, pulling her up to his face much to the shock and aghast of the others. "What I want is the demon slayer's sword! The Nichirin Blade! Give it to me now!"

"That is enough." the girl with the blindfold appeared beside the scarred boy and gently pried his arm away from the girl's head. "They just explained that we will receive our swords within two weeks. Please be patient."

"I don't care!" He pried his arm out of her grasp. "I want the sword now! How else would I kill Demons without it?!"

"I understand. But they are simply explaining our duty as Demon Slayers." She stood her ground. "It would help if we waited for them to explain everything." The boy growled and looked ready to throttle her. Tanjiro looked on with worry and was ready to intervene, but the blindfolded girl's hand went to her sword. "Cease and desist this action immediately." she advised. "Any further, and I will use force. Choose wisely."

The boy glowered but realized he was outmatched either way. He reluctantly backed away and rubbed his arm.

"Are you finished?" the girl with black hair asked. "If so, please go over there." She gestured to the table behind them. On the table was an assortment of chunks of metal. "The alloy you choose will become the sword that you will wield to defend yourself and destroy the demons. You must choose which piece will become your sword."

'They are so many.' Tanjiro looked at the chunks of metal, unsure which to pick. 'I don't know anything about these metals, and they all small the same. Does it matter which piece we pick? How is it going to affect our swords?' In the end, he still had no answer. Instead, all he could do was trust his instincts.

His hand reached out and grabbed hold of the piece of his choice. The rest soon followed.

The five newest members of the Demon Slayers Corps had dispersed and left Fujikasade Mountain, no doubt returning to their homes and rest, then train and await for the arrival of their swords. As the twins explained to them, once they had both their uniform and sword, they would begin their missions as demon slayers immediately.

Before 2B could leave for her temporary residence, however, one of the twins had walked up to her. "Please, wait a moment." The former android looked at the small girl in confusion. "Our otou-sama would wish to speak with you, Tsukiko Yona-sama."

"Your otou-sama?"

Why would this girl's parent wish to speak with her? Moreover, who was her father anyhow? Now that she thought about it, she still did not know the identities of the girls. Considering that they were supervising the Final Selection, and given that the Demon Slayer Corps trusted them enough to oversee it, they must hold some kind of sway within the organization. The first such individuals that came to mind were the Hashira - the strongest demons slayers within the organization that answered directly to the leader of the Demon Slayer Corps, Kagaya Ubuyashiki.

Either way, 2B saw that she was really in no position to refuse. It wouldn't do well for her to deny such a request, regardless of who their parent was. She gave a small nod and followed the girl. She rejoined with her twin sister, and the three made their way down the mountain. A small carriage was waiting for them, where a man stood guard waiting for them. As soon as she saw him, 2B grew tense.

A heavy mist surrounded him, thick and violent like a storm. His body had numerous scars, the most prominent being the ones on his chest and face. His white hair was wild and his eyes looked manic, yet there was clearly a sense of clarity in them. He wore the uniform of the Demon Slayers, but over it was a white haori, implying that he was of a higher rank than she was. At his hip was his Nichirin sword.

The man's eyes zeroed in on her. "You're the girl. Yona, right?"

"Yes." 2B replied. So he already knew about her? And from his tone of voice, he did not seem to have a good view of her. "And you are?"

"The name's Sanemi. The Wind Hashira." He grunted. "Oyakata-sama requests your presence." He opened the carriage door. "Get in."

She was stunned. A Hashira was here? She glanced at the girls beside her, who smiled and thanked Sanemi. In contrast to his attitude towards her, Sanemi smiled gratefully back at them with all due respect. Then his previous words registered.

Why did the leader of the Demon Slayers want to speak with her?

It took three days for the carriage to arrive at the estate where Kagaya Ubuyashiki resided. And as 2B expected, it was as large as it was beautiful. It wasn't the size of a lord's castle, but the grounds it sat on was enough to fill the field of a common lord's territory. She had half a mind to wonder what use such a large facility would be to a man, aside from a massive statement and testament to his influence.

She did not have time to stare at the mansion's exterior for long as she was soon ushered inside and led into what she assumed was the main complex. Sanemi led her down the halls with his back facing her. During the whole journey, he rarely ever spoke to her, and whenever he did, he made it clear that he did not appreciate her presence for whatever reason.

She had a good idea why. Isshin had told her that not many in the Demon Slayer Corps would appreciate her using the Breath of the Moon, and obviously Sanemi knew she was a practitioner of the style. How he knew that, she had no idea.

An idea came to mind as they walked. Was it possible that Ubuyashiki wanted to speak with her regarding her usage of the style? Would he shun her or remove her from the organization based on that fact? She doubted this was the case, seeing as how there were still people who used it, albeit very few. According to Isshin, following the passing of her father and her taking up the style as her own, there was only a meager handful of people who still utilized the Breath of the Moon. Some of those users were still active members of the Demon Slayer Corps, so the idea that Ubuyashiki would ostracize her simply for that fact alone was not possible.

That only raised further questions of course, yet she knew she would soon discover the answer soon enough. After a minute or so of walking through the halls of the estate and its main complex, Sanemi stopped in front of a pair of elaborate doors with vibrant designs, cherry blossoms and koi fish printed on the front.

"Oyakata-sama." Sanemi kneeled in front of the door. "I've brought Tsukiko Yona, as requested."

"Thank you, Sanemi." a gentle voice called out from beyond the door. "Please, send her in."

Sanemi turned his head to 2B. "Be sure to give your proper respects, girl." he warned. "Disrespect the master, and I will see to it you pay for it."

"Understood." 2B replied calmly, unfazed by his hostility. She took a moment to compose herself, then opened the door and stepped inside.

As soon as she was within the room, the door closed behind her. But that small fact did not bother her for her attention was focused on the person before her. In contrast to her initial thoughts of the Head of the Demon Slayer Corp. being a man in his later years in life, Kagaya Ubuyashiki was a man no older than his mid twenties. He was dressed in a black yukata with a white haori with flame motifs on the edge. His hair was black and cut around his neck. But what stood out to 2B the most was his face. While he was definitely attractive, her focus was not his physical beauty, but the fact that the upper half of his face was scarred over. The flesh was discolored and looked as if it was rotting. His eyes were blank and glassy, indicating he was blind.

The mist surrounding him was like a rainbow, ever changing and beautiful. It also carried a strange scent, putting her at ease for the first time in what seemed like years. The idea that she would face combat seemed so far away. Yet that odd feeling of peace came to an abrupt end when she realized what was happening and reclaimed her edge. She could not afford to be lax or comfortable. She must remain vigilant, even in the presence of someone like this.

Kagaya Ubuyashiki did not address her immediately. He sipped the teacup in his hands, savoring the taste of the drink before he gently sit down on the mat.

"...I believe that this is the first time we've met, is it not? Tsukiko Yona?"

"I believe so." 2B replied curtly.

The man smiled kindly. "Please, take a seat." Though hesitant at first, she obeyed and approached. She gently set herself down in front of her, knees pressed against the tatami mat. "I am sure there must be many questions you have, such as I why I called for you out of everyone who succeeded in the Final Selection. But before I get into that, I must ask you. How is Isshin doing these days?"

2B blinked beneath her blindfold. "You...know of my Ojii-sama?"

"I remember the names of every one of my demon slayers, whether they are still under my employ, dead or retired." Kagaya answered. "Isshin was one of my favorites, truth be told. In the admittedly short time I've spent as the 97th leader of the Demon Slayer Corps, I've never met a man so devoted to the cause. To his allies, he treasured them as if he were family. To the demons, he may as well have been the shinigami himself. I whole-heartedly believe he was worthy of the position of a Hashira, but he ultimately declined. He was rather humble then as well."

2B smiled slightly. "Yes, he is. Though I'm afraid he has become quite the grouch in his old age, as well as a stern teacher."

"I imagine so." Kagaya chuckled. "May I offer you some tea, Yona?"

"No. I am fine. Thank you for offering."

The man nodded. "Very well. I suppose we should move past the pleasantries and get to the heart of the matter, then. I imagine you must be wondering why it is I've asked you to come here."

"I have a good guess as to why. It is because I practice the Breath of the Moon."

Kagaya gave a strange smile before he looked to the side. In open view, there was a beautiful stone garden with a small pond surrounded by rocks. The sky was painted clear blue with few clouds above. Combined with the peaceful nature that surrounded Kagaya Ubuyashiki, 2B wondered if this could be called a scene in heaven. "The Breath of the Moon was among the many styles developed by the first Demon Slayers." he said. "Much of our records pertaining to that time have been lost, including the identity of its creator as well as the lost style once used by the very first Demon Slayer himself. However, what little we do know is that the man who created the Breath of the Moon betrayed his comrades and students by becoming a demon, falling sway to Kibutsuji Muzan."

"And as a result, those who practiced the Breath of the Moon became ostracized." 2B continued sadly. The image of her father flashed in her mind, dying and suffering from his wound with sword in hand. "Though they fought for the sake of defending mankind from the demons, their comrades were angry that they would continue to use techniques that were made by a demon."

"And the results of such alienation can still be felt. Including yourself, there are only ten people in the world who still use the Breath of the Moon." Kagaya looked back at her. "Tell me. Why did you decide to choose the Breath of the Moon?"

At this, 2B fell silent as she looked to the stone garden. Memories from years ago flashed by in her mind, back to the days when she first began her path to once again defending humanity from those who dared to wish them harm.

Nine Years Ago...

Shanghai.

Compared to Japan, which had was still in its infancy regarding its subtle changes towards westernization cultures, one of the municipal cities of China was well in its way. The streets became paved with cobblestone and railroad tracks. Buildings that were once made of tiled roofs and mud huts became replaced with bricks and stone. Steel poles were lined against paths next to the street made from concrete, bulbs attached to the end of each pole. Everyone, sans for a few odd individuals, were wearing western clothing such as suits and dresses.

The ship docked and set its ramp down, allowing its passengers to disembark. Among those passengers was a little girl, 11-year-old with icy blue eyes and snow-white hair. She was of Asian descent, wearing a small white yukata while carrying a wooden box in her tiny arms. Though she had the appearance of a child, her eyes told a different side.

The presence of a young girl with seemingly no one there at her side was enough to raise some concerns. Many questioned if she was an orphan or if she was lost. Others believed that the girl was a runaway, escaping a harsh life in exchange for a better one. However, there were some who held the girl with some hostility when they recognized she was of Japanese heritage.

The relationship between China and Japan has always been strained. Several events in the past had left both countries viewing each other with caution, though the inclusion of western culture and trading was perhaps the biggest cause of concern as Japan slowly and forcefully began to push its change to westernization onto them. One account said that Japan viewed China as an "antique" culture. This was but one of the many reasons why China and Japan hated each other, and it would surely not be the last. And as one might imagine, a person of Japanese heritage was usually met with hostility or suspicion.

That same treatment was extended towards children as well, though notably there were less people who treated her with such open anger. After all, she was a child. Japanese she may be, it was not as if she could help where she was born.

She was here for one reason and one reason only; to find her remaining family. Her father had planned to take her and travel to Shanghai for a new start after her mother's death.

However, due to the demon attack and her father's unfortunate demise, plans were changed. Seeing as her only family was in Shanghai, she made her decision. Certainly she could've remained in Japan by living with one of her neighbors, but none of them could offer what she sought. With demons on the prowl, she needed a means to fight. To fight like her father had in that one, brief moment. Surely her uncle had the answers.

Admittedly, it was a shot in the dark doing this. She had little information about her uncle, but what info she did manage to acquire from her parents' closest friends, he used to be a swordsman but did not serve under a lord or work for the government. Despite that fact, he was given a rather handsome salary and lived comfortably before he ultimately decided to rest his laurels and take up a life of comfort as a merchant in Shanghai. Assuming he was indeed a Demon Slayer, the same as Gyomei, perhaps he could offer her some form of training.

Of course, there was no actual guarantee her uncle was a demon slayer. This was all conjecture, but it was all she had. Besides, she had no other family. As the remaining heir of her bloodline, she would be expected to uphold it, however much it was worth in the grand scheme of things. In all honesty, 2B did not understand why bloodlines were so important to Japanese culture. Why was one's blood important when it came to matters such as political power, prestige and recognition? Was there some kind of underlying meaning that she could not see?

As the young girl disembarked and entered Shanghai, ignoring the odd stares she received along the way, 2B couldn't help but notice the faint mist that surrounded the city. It wasn't bloody red like the ones that lingered around the demons, but a mixture of colors. So disorienting was the clash of colors that she couldn't help but wince.

Ever since that fateful day a year ago, she saw these colorful mists lingering around people. She did not understand why she alone saw them, only that they somehow represented something. The intensity of the mist, its thickness, its color; all of these things gave away something about the person it lingered around that told her what she might expect. If the mist was thin and almost transparent with a soft or light color, then the person was sometimes meek or shy, but overall kind. If the mist was thick and heavy with a darker color, the person was likely to resort to violence easily. Those that were in between were mild-mannered, but otherwise had a hidden side to them.

She also noticed that almost none of the people she saw had that silvery mist like her father did. As to why that was, she was not sure.

2B did her best to ignore the pain the clashing colorful mists around Shanghai's residence caused her while she searched for the estate where her uncle was believed to be residing. It took her an hour of wandering and asking for directions whilst also avoiding some of the more unsavory characters before she finally discovered his location.

She realized her uncle had a handsome salary and likely amassed a fortune due to his occupation as a merchant, but she never expected for him to be living in such a grand place of residence. In terms of western design, it wasn't as grandiose as a mansion, but the elaborate design of use of concrete and wood certainly made it rather interesting. Pillars were used to uphold the roof of the front entrance while beams made entirely out of stone could be soon on the building's exterior, reaching all the way up to the tiled rooftops. The house extended at least six or seven meters on each side, two-stories tall with windows hiding the interior with dark blue curtains. There was a small but sizable garden sitting off to the side, while the entire premises was defended by stone walls and a steel gate, which 2B currently stood in front of.

"I see the life of a merchant and being funded affords a life of luxury." 2B noted to herself. "So this is what being rich looks like." She pressed her hand against the gate and slowly pushed it open with some effort.

The property between the gate and front door was a beautiful landscape. There were flowers planted across the walkway and various other plants that she couldn't quite identify. She approached the wooden oak door. Much to her chagrin, she could not reach the knocker that was danging in the middle of the door due to her short height. Instead, all she could do was knock as hard as she could without seriously injuring her hand. She gave three sharp knocks, then waited for a minute patiently. Just as she was about to knock again, the door opened to reveal a woman with dark hair and violet eyes, wearing a kimono with a yellow sash.

She blinked in surprise when she saw 2B, a mere child at the doorstep of a merchant. "Oh my, what brings you here, child?" she asked curiously.

"I am Yona." she greeted. "Is Isshin-dono home?"

"Oh? Japanese? So you're little Yona?" The woman questioned.

2B nodded in response.

"I see. Please come in, come in." She guided her into the household.

Yona bowed her head in gratitude, then stepped inside.

The man that was her uncle was her father's older brother. He was twelve years older than Yukito Tsukiko and was described as being of the stoic sort. At times he could be a drunkard, but above all else he was a family man. He never married because he felt that no woman could ever be attracted to a man who preferred to swing his sword at others, but that was not to say he was not attracted to the fairer sex. In his teenage years, 2B's uncle was said to commit acts of philandering and was known to cause trouble by courting the daughters of influential families in the region, only for said relationships to be casual with no actual meaning. The amount of trouble he caused was certainly troublesome, but each time the family came looking for revenge, they were met with steel. Especially when the offended parties attempted to hurt him by attacking his own kin.

Her father spoke very little about his brother, but meeting him personally, 2B couldn't help but compare him to Commander White in terms of intimidation factor. Though he was now at the ripe age of sixty, his hair developing large stripes of gray and wrinkles blotting his skin, his body was as fit as an athlete and his hands looked rough. He was old, but at the same time he was still full of vitality and fully capable of combat. The way he carried himself implied discipline, and the steely look in his eyes would have petrified a lesser man. A salt-and-pepper beard covered his lower chin, closely shaven but still long enough to hide his wrinkled skin. His yukata was dark with golden decorations along the left side.

The moment she entered the room, she could only feel his eyes bearing down on her and determining whether or not she was a threat. In response to such evaluations, 2B steeled herself and was ready for a battle at the drop of a hat, clutching her grandfather's blade with the intent of unsheathing it. She never once turned away from his eyes and returned the look, daring him to attack her.

She was no fool. She would certainly lose, especially in this weak body of hers, but she'd be damned if she would not go down without a fight.

"...heh. Good to see Yukito's brat grew up strong." A crooked smile adorned his face, pleased by what he had seen. The pressure that fell on the room dissipated and she relaxed her grip. "Yona-chan, right? It's been so long. Last time I saw you must've been, oh, maybe when you were still in your mother's womb. I suppose you know who I am already, but my name is Isshin. It's finally nice to meet you in person." His smile dimmed and his eyes turned misty. "A shame it had to be under these circumstances. How long has it been since...?"

"Fourteen months, six weeks and three days since my father's passing." 2B informed him. His eyes widened in surprise, not that she blamed him. After all, who expected a child to count down the days since the death of her family? "I spent that time under the care of one of otou-sama's close friends. I believe you received my letters."

He nodded. "I have. They give you any trouble?"

"None at all, though the village has been in dire straits since it was discovered that the village head was a demon."

"Understandable. Given the circumstances, anyone would feel the same." To learn that the leader of a village became a Demon and feasted on his fellow villagers while everyone was unaware. It was a terrifying thought. And to think there was another during the attack. "...And you said you were saved by a Demon Slayer who was fortunate enough to find housing with you and Yukito, correct?"

"Yes." She nodded. "He slew the village head...but we didn't realize there was another Demon until..."

secs agoShe trailed off as the memory played out in her mind. Those foreign, human emotions rose within her again and created no end of discomfort for her. She tried to quell the emotions, but only partially succeeded as they surfaced on her face for a brief moment. Her uncle nodded in understanding. "I see. Still, what made you decide to suddenly come here to Shanghai?"

"Because I wish to ask you something, Ojii-san." 2B told him. The man raised an eyebrow, curious when he saw her serious expression. "Were you a member of the Demon Slayer Corps?"

Her uncle chuckled. "I was, but that was a long time ago. And I believe you just answered my question. Still, I'll ask again." He leaned in, a strange gleam in his eyes. "Tell me, Yona... Why have you come here, to this hellish city?"

2B bowed her head deeply and begged. "I beseech you, Ashina Isshin. Please, teach me how to become a Demon Slayer."

AUTHOR'S NOTE: Drat. I was three days away from making it in time for Christmas. Oh well. Special thanks go to Daemon of Wrath for helping me complete this chapter.

Quick clarification that this is strictly a Kimetsu no Yaiba x NieR crossover. The character Isshin Ashina is based off of the character of the same name from the game Sekiro: Shadows Die Twice, but they are not the same person. Also, regarding the "vision" that 2B sees that helps her see without actually using her eyes, think of it like a bastardized version of the "see-through world." It isn't as effective, but it helps 2B out because it also helps her see things most demon slayers might not see. Granted, her "sight" isn't as good as the "see-through world" that others with the mark see, but it works well enough.

Another interesting to note is in regards to 2B's techniques. Seeing as how she is not a demon and lacks the abilities that Kokushibou has, she needs to use two swords to accomplish certain techniques. She's learned how to dual wield, but for the most part, she will only draw the sword on her back to use certain techniques. Also, be sure to remember that, in contrast to the raw power of the techniques Kokushibou uses, hers are nowhere near as powerful.

Also, regarding who 2B will interact with the most, I've decided to have her partner with Zenitsu. I don't really feel like rehashing canon events, the Final Selection Arc being the sole exception because it also gives you a glimpse between 2B and Tanjiro's future interactions and differing ideals.

On a side note, I finally got my hands on The Last Word exotic in Destiny 2. It's about damn time. Now all that's left for me is Thorn, Sleeper Stimulant and Malfeasance. And maybe whatever new Exotic I'm looking to get my hands on that doesn't require me to do a Raid. For the life of me, I can't form a party to save my life.

I hope everyone has a wonderful New Year, and on that note, while a few days late...

Merry Christmas, you filthy animals.

REVIEWS

Donjusticia: Warning. counter measures shall commence in T-minus X seconds. Please evacuate the facility.

Dxhologram: Perhaps, but she spent a majority of her life as a machine. Even though she's had twenty years, she's still learning how to understand and deal with humans. It's gonna be a while.

Guest (RedSazabert): Spoiler, expect either a mean right hook or a ten out of ten German suplex to occur within seconds of their first meeting.

The Neckbeard Knight: I contemplated giving 2B an original Breath, but ultimately decided against it. I felt that Breath of the Moon would have been a better choice, not to mention the fact that 2B's "home" was the moon itself.

Kensei-1085: She is not a descendant. She's simply one of the few people who still practices the techniques he created.

Yolea Irk's: That's a relief to hear. Hopefully, I can continue to get 2B's personality down pat while also helping her grow more as a "human."

fruitspunchsamurai-987: Indeed. It will definitely be interesting, learning how to write her character as a human instead of as a machine, which brings a whole lot of new things to consider.

Killer Hamster: As you can see, 2B's story is concurrent with Tanjiro's own, but she has five years over him since as of Chapter 2, 2B is now twenty years old.

Hakuryukou79: Indeed. Sanemi's already shown he doesn't have a good opinion about her, but that may change over the course of the story.

Guest #1: There is a reason why Dishwasher1910's artwork is used as the cover.

NoNameAvailable Bis: 2B's relationship with humanity is complicated, yes. Not that you could blame her, considering she was fighting for a race that's been extinct for who knows how many years. However, as they keep saying, feeling emotions is forbidden or something along those lines. Despite her feelings, her purpose for fighting is hardwired into her, reincarnation or no. Even if her feelings towards humanity may be complicated, she can and will fight to protect humanity. Of course, its coming to understand humans as well as the humans who've become demons themselves that will be the major points of development for 2B during her career as a Demon Slayer.

Guest (Andromeda): 2B will eventually become a Hashira, and yes, she will be the Moon Pillar. Fun fact: Her Hashira look is what is depicted in the cover art.