It's simple.

Reincarnation.

There were no dark tunnels with a bright light in the end. No Shinigami slicing through a cooling body and eating its meal. No family waiting by a campfire, ready to either hug or harm.

It's simply the feeling of death warming over your skin. Your aching heart beating slowly to a still. The sight of your brother, feeling you with joy, pain, guilt, love, and every other emotion your body can handle, being the last...

Until you blink.

It's disorienting.

Knowing that you've fallen just a second ago but are now standing. Feeling the ache of a long battle in your bones but feeling refreshed yet weaker than before. Being surrounded by nature but finding yourself among a technologically advanced cityscape.

If life was more complicated, panic would have settled in. Thoughts of where he was, what happened to him and his brother, would have been in the forefront of his brain.

Life, however, is simple.

Or at least, simple for someone born and raised in war, and had lived a life filled with battles and death.

The sight of an enemy, a green slime creature with one of its many tentacles raised to hit him, and a victim, blonde haired male with a fearful yet furious glare, halted any reflecting thoughts he had and brought forth a heavy focus on the present, along with an instinctual mindset to fight for his life and for those around him.

Similar to most of his fights, he blinks and feels the somewhat familiar ache in his eyes, less painful and hazy than a minute ago.

Green eyes bleed, changing to a bold red. Along with the color, three black comma marks appear, swirling around his pupils before slowing down to a stop.

Sharingan.

Time slows down and he takes note of multiple things at once. The incoming tentacle. The vulnerable eyes and mouth of the slime creature. The shock in the victim's eyes. The slack jaw of the lanky blonde bystander. Several costumed folks running towards him.

He twists to the side to dodge and it's awkward.

His current body is shorter, skinnier, and far slower than what he's used to. What should have been a clear dodge ended with the tentacles barely grazing him. He immediately takes note of his speed and calculates it into his next actions.

Left arm jabs forward, index and middle finger aiming for the vulnerable eyes. When it meets its target, he twists again, facing him and his right arm follows the movement. Clenched fist is aimed at the slime creatures mouth, punching inside and up.

The enemy chokes and stumbles backward, allowing him to grab the victim by the back of his shirt and pull. His strength is comparable to a ninja academy student at best and civilian at worst. When the tug results in nothing, he attempts again, this time with chakra enhancing his strength.

The victim flies towards him and he's quick to grab and push him behind. No matter how strong the explosions this boy can create in his palms (and what a curious Kekkai Genkai that is), the boy's too young, too rowdy to know how to properly fight, and he moves to protect him.

"I'LL KILL YOU FOR THAT, BRAT!" shouts the slime creature, hatred in its reddening eyes, as it lunges forward.

Snake. Ram. Monkey. Boar. Horse. Tiger.

Mental experience and physical inexperience wage war against the other as he clumsily forms the signs his clan prided itself on. With a deep breath and energy churning in his lungs, he's ready to unleash a fire to burn this enemy but before he could do so, the blonde bystander appears in his view once more- this time in a transformation dissimilar to a henge.

"TEXAS SMASH!"

The man punches the slime with enough strength to cause winds to rush through the alleyway. Feeling the urge to release the fire chakra gathered in his lungs, the sharingan user thinly exhales, allowing the winds to erase any evidence of his fire.

As the street darkens, he looks up, watching clouds close in together and rain pouring in. He's seen the man's punch. Watched as an unusual rainbow colored chakra gathered at the edge of his fists before being released. His own fists clench, wondering if he could recreate the same technique at a later date.

Not now.

Focus on the mission.

With a quick shake of his head, the Uchiha deactivated his Sharingan before glancing back at the blonde kid he saved. Lighter red eyes glared at him, more so when he smiled back.

Cute.

He almost looks like Sasuke whenever the youngest Uchiha heir heard that the two Uchiha prodigies were assigned a mission. Except less cute pouting and more vicious growling.

Before he could check on the kid, he was swarmed by those weirdly costumed folks. Half praising him for his abilities and for rescuing the kid, while the other half scolded him for entering the fight. He barely listened to them talk, not after he heard them talking about heroes and how it's their duty (not his) to fight the villain. The infamous Uchiha scowl formed on his lips, followed by a blank expression. He's not the smartest person in the village, that title belonged to the Sandaime Hokage, but he can pick up a few context clues.

The word hero is different in this world. Where in Konoha and the other hidden villages, it meant a shinobi who protected the village or a person who saved another. In this world, it meant an occupation. Their definition of a hero became clearer when some of them moved towards the civilians, soaking up their praise. His scowl deepened.

While the definition for hero differed, their actions are similar to those who became a shinobi for fame. Hero. Shinobi. They're similar occupations with similar mistakes, losing their true meaning and purpose against fame and fortune.

He swiftly turns around and with a quick hand sign, index and middle finger straight up and the rest of his fingers curled towards his palm, disappears from view.

The blonde bystander, the same skeleton-thin man who stared in shock and the same buff man whose punch changed the weather, stares at the empty space in the alleyway with wide eyes before excusing himself.

A heavy huff of dissatisfaction escapes his lips, followed by a self-mocking laugh.

His stamina... sucks.

Sharingan. Basic chakra enhanced strength. Shushin. Two were moves commonly used by Genins and all three were learned by any decent Uchiha by the time they've unlocked the Sharingan. He's been able to use them with ease since he was seven and yet now...

Settling in his seat upon the roof of a random house, the reincarnated Uchiha sighs. His journey away from the crowd was made passing by multiple windows that reflected his current form. Messy green hair. Green eyes. Slightly dirty clothes. And a skinny body underneath.

It tells a basic story of this body's life.

His clothes aren't dirty enough for someone poor nor is the cloth well made for someone rich. Similar black clothes were seen worn by several young males throughout his journey to indicate uniform- they either worked a common job or were a civilian student. Skinny build could be attributed either to a physical condition (which he doubted), a slightly poorer than normal income (which he can almost agree upon), or a mix of different scenarios (a possibility).

In short, he was occupying the body of a young man about his age, middle class, student or common worker, and as unathletic as a civilian can possibly be.

Not enough information.

With a disappointed click of his tongue, the teenager pats himself down, searching for any identification he could find.

Nothing.

The only thing he was carrying was an ink-carrying object (which he can use to write), a square cloth, and a weird-looking pouch that had the blonde man from earlier's face. Inside it were bills and coins from this world's the pouch back inside his pockets, he rolls the sleeves of his black uniform, exposing his forearms and shins.

There.

His bare arms and legs showcased a detailed story.

Pale skin was covered with bruises and burns, all in different stages of recovery. Hands smooth, if not a bit marked with ink. His muscles differed in shape. The ones in his arms were as skinny as it could possibly be, except for his right hand. While his leg muscles were defined.

A writer, definitely. Unless there's an instrument that can be played with one hand but that wouldn't explain the ink nor the ache in his right palm. The lack of definition in his arms meant that the kid barely lifted things. Lack of calluses in his knuckles meant that he didn't fight- which also meant that the situation he found himself in earlier was rare or new. The muscles in his legs could have meant a mostly leg-based fighting style (not possible with his skinny arms) or a runner .

As for his injuries, they're not self-inflicted nor do the injuries match any fits of clumsiness. The scars are in different stages of healing for it to be a major attack they found themselves in the middle of. Conclusion, a deliberate and constant attack. Probably inflicted by someone close to them. Family? Friend? Teammate?

A teenaged civilian, student or common worker, living with a middle class income, wrote either as part of his job or hobby, runs weekly or almost daily, and is constantly attacked by a person they often meet.

They're not enough to sate his curiosity but it's more than he expected, more than what he's given during ANBU missions.

Allowing himself to be satisfied, for now, the Uchiha lays down against the tiled rooftop and wonders about multiple things. Thoughts previously withheld gushing in: Where he was? Who this body belongs to? Why was he here? Is this him being reincarnated? And if so, why at this age and where were his memories?

A green eye flickers to a blood red color and back to green again, leaving behind an ache.

The one thing he doesn't have to wonder about (and thank kami for that) is what's happening back in Konoha. Twice since he appeared in this world, his left eye would ache and he'd see an opaque vision of his brother talking to him.

He's certain... as certain as he can possibly be that those visions weren't a part of his imagination. Never before has he seen his brother's eyes so sunken in, the frown of his lips that deep, his shoulders slouched in a manner unbefitting their Uchiha name. He carried the sins of their clan on his shoulders. Sins that he once carried alongside him.

There's a chance that he wouldn't be able to come back. Wouldn't be able to lift the weight off his brother. He died a certain death, there's no chance for resurrection, only for reincarnation. The shinobi within him knows how to cut off his losses, to be grateful for the minor things in life, and so he's thankful for his ability to see his little brother's actions instead of being stuck in this world unsure as to how they are.

"DEKU! WHERE THE FUCK ARE YOU, YOU PIECE OF SHIT?"

Even with his eyes closed and his body pressed against the rooftop, hidden from the streets and the streets hidden from him, the Uchiha prodigy could feel a semi-familiar aggressive aura moving across a nearby lane. It's the younger blonde male from earlier, the one stuck inside the slime villain.

To think they'd be near each other again.

Another semi-familiar aura enters his senses, causing him to smirk and repeat his earlier thought.

While the kid passed by, stomping all the way and never looking up, the older blonde after minutes of searching the area accidentally looked up and caught sight of a pair of green eyes observing him.

"Young man! I've been looking everywhere for you!"

His voice, while not as loud as his muscular form (most likely a hero persona he projects), is loud and boisterous compared to normal folks. The man waves energetically at him, beckoning him closer.

Nodding, he pushes himself up, hands absentmindedly brushing off the dirt clinging to his uniform, and jumps off the roof.

"Ukk..."

Blood spills from All Might's mouth, sunken eyes wide in shock. His lanky frame rushes forward to catch the falling teen. As arms reach up to grab him, the shinobi lightly kicks them away before gathering enough chakra to reinforce his legs and land in front of the hero.

"All Might..." he greets, taking out the square cloth in his trouser pocket and offering it. It's immediately waved away.

"I'm fine, young man. Just shocked," he coughs lightly to get rid of any blood left in his mouth, "I've never seen a kid do that before..."

"You were looking for me?" he repeated with a questioning tone.

"RIGHT! Young man, I came to thank you and to also discuss your question from earlier. If you hadn't been there, if you hadn't told me about your life, I would have turned into a man in a bodysuit who was just all talk... so thanks."

Question? Earlier?

Green eyes widen. This man... He's talked to whoever's body he's inhabiting. Lack of familiarity meant that they weren't close, but to give out the story of his life...

Then again, he's seen people willing to give those out when they're in need of guidance, and All Might, from what he knows, is a known and famous hero. Similar to the Hokage and any Elite Jounin, as well as any old human, his hero status screams out knowledgeable for those inexperienced in life.

"You're welcome," he replies with a slight hesitance, mind buzzing with do's and don'ts. There's no instruction on how to prevent people from realizing you're an imposter or an amnesiac (he can't count that theory out yet) so broad answers would do well until he has more detail.

"I have to ask. Your Quirk..."

"My quirk?"

"You told me you were Quirkless but I saw it, you had red eyes and teleported."

"My Quirk..." the Uchiha pauses, gathering as many facts as possible to find an answer.

The facts are, Quirks (with a capital Q) is another word that changed definition in this world, him mentioning Shunshin and the Sharingan meant it either involved his Kekkei Genkai or jutsus in general. Quirkless probably meant a lack of jutsu? The punch All Might did involved a rainbow chakra and the civilian before had a chakra mostly centered in his palms and lingering in his skin... most likely its lack of bloodline but he wouldn't be surprised if his previous idea is true.

"It just appeared."

He watches as the blonde chokes on his own saliva (and blood) before chuckling to himself.

"You continue to surprise me, young man, but I should have expected your answer. You were too honest earlier and you had nothing to gain for lying. Plus, I doubt a fanboy like yourself would have lied."

Fanboy?

... Great.

Shinobi training prevents him from accidentally showcasing his feelings, he doesn't shudder recalling memories of being chased around by fangirls nor does he scowl at the idea of acting like them. Instead, he smiles politely and shrugs.

"It's probably one of those late blooming quirks or a situational quirk..."

"Strong emotions?" he interrupts, grasping the idea given to him and wondering if, just like the Sharingan, his reincarnation here was unlocked by a strong emotion.

Most Uchihas unlocked their Dojutsu due to battles, due to a desperation to survive, and he's already concluded earlier that this body is new to fights due to its lack of calluses. Maybe getting into a fight, being desperate to survive, unlocked his reincarnation?

Too theoretical. It's a desperate guess for his appearance here.

"It's possible. If the emotion is too specific, an emotion 4 year olds wouldn't have, your quirk wouldn't appear until later."

A grin stretches across a thin face, sunken blue eyes looking at him with amazement and pride.

"But back then, before you gained your quirk, timid, quirkless you acted when other heroes wouldn't. And it's because of your actions at the scene that I was able to act."

Lips tilt upward, glad that his body's owner was willing to fight an enemy that heroes wouldn't, even if they were a weak civilian. Self-sacrifice. A person who protects peace. If they trained their body, they could become a true shinobi.

"There are stories about many heroes, how they became great. Most have one thing in common- their bodies moved before they had a chance to think, almost on their own. And today... that's what happened to you, young man. You too CAN become a hero."

A fond smile forms.

Those words... they're similar to the Hokage's words, to the Will of Fire. A part of him is glad that this world holds a similar idea, of protecting those precious to them- including civilians. While a part of him feels guilty. All Might's words held a lot of weight and was clearly intended for the quirkless civilian whose body he occupies.

His sharingan appears once more, memorizing every part of the scene- the hero's emotions and stature, the sunset, the wind coming through the streets. He wouldn't be able to recreate it perfectly but once he's able to, he'll make sure that the civilian would see this sight and hear those words said back to him. It's the least he could do for the brave kid.

"I deem you worthy to inherit my power, my Quirk is yours to inherit."

Wait...

What?

So Quirk is a Jutsu? Not a Kekkei Genkai? The word 'inherit' implies that it isn't a normal jutsu, however. Is it a Kinjutsu or a forbidden technique? Maybe a secret technique only passed on from mentor to student- like the Yondaime Raikage's Lariat or the Yondaime Hokage's Rasengan?

"Listen well, young man. You need to decide whether or not you will accept my power!"

"Your quirk... your power... what...?" is it? No. He can't ask that. His body's a fanboy. Surely, he'd know almost everything about the hero. If his experience with fangirls can be used as a reference, the boy's probably stalked All Might before and knows uncomfortable facts about him, such as underwear or training areas.

"The tabloids called it 'superhuman strength' and a 'boost' and I constantly dodge any questions related to it during interviews with a funny joke because the Symbol of Peace, All Might, had to be thought of as a natural-born hero. But young man, I will tell you the truth..."

The urge to use his Sharingan for this whole conversation grows. Not only did he miss an important moment he would need to use as a Genjutsu in the future, but this talk is something he'd need to rewatch again and again. If only this body had enough stamina to maintain the Sharingan for a long period of time. He has enough for a minute or five, but he's saving those for emergency reasons.

Grabbing the ink-carrying object from his front pocket, he discreetly placed his hands behind his back, writing the words 'Quirk', 'Symbol of Peace', and 'natural-born' on his free palm. This body may not be satisfactory for his shinobi needs but its steady writing hand is perfect for this.

"My quirk was passed on to me like a sacred torch!"

All Might's grandiose movement, spreading his arms wide, told him of his statement's importance. That passing on quirks is rare, possibly unique. Following this hidden hint, he asks for further explanation...

"Passed on to you?"

... and doesn't get it.

Instead of an explanation, the blonde hero nods eagerly and replies, "And next, it is your turn. I can give you my abilities."

Scowling softly, green locks fall down his face as his head nudges to the side and repeats the same question, earning a confused look.

"What?"

Green eyes narrow.

"Ah! Right! The true name of my power is 'One for All'." A familiar rainbow chakra appears in the man's skinny and calloused palms. "One person cultivates the power, and then passes it to another person, who also cultivates it, then passes it on and it continues to grow as it gets passed along. It is the crystallization of power that spins together the voices of those who need help with a courageous heart." He finishes with a flourish, clenching his hand and stopping the rainbow chakra from appearing.

All Might's fond of dramatics, he thinks. His actions, his words, they were unnecessary displays but it could have been worse. Every ninja has their weirdness, Jiraiya-sama with his pervertedness, Gai with his green leotard and Youth speeches, Hokage-sama with his love for Icha Icha... a bit of dramatics is bearable compared to them.

"Why are you giving me this?" he questioned.

"I have been looking for a successor, and then, I watched you jump into action while the rest of us stood idly by," an utterly serious expression occupies the hero's face, "You're just a Quirkless hero fanboy but you were more heroic than anyone back there! Well it's up to you though. What'll you do?"

He hesitated. This question isn't for him but for the fanboy who jumped in to save a person. The Quirkless civilian who truly doesn't have any powers. If he denied this, the teen might never get a Quirk and become a hero (unless he wants to go through the Taijutsu spandex route). Accepting it, while more tempting than the other choice, had its own problems. What if he ends up stealing this from the kid? What if he didn't want it?

The definite choice is to wait, to see if he'd gain memories or if the kid will take back this body. But how would he be able to get All Might to agree on waiting for an answer when he's been eagerly looking for a successor?

The answer to his question doesn't pop up from his mind. Instead, it came from the hero himself.

"Well, young man?"

Young man.

Ever since they've started talking, All Might's been calling him 'Young man', never referencing a name. Even he, the stranger that he is, has called All Might by his name- as weird of a name as it is.

He wants to both laugh and shake his head in disbelief. Here was the 'Symbol of Peace' offering a stranger a power that he could easily guess as undeniably powerful.

"Do you even know my name?"

The resulting silence after his question made him scoff lightly in amusement.

"Uhh... I..."

All Might looked as if he'd been stopped in time, barely moving except to blink. The silence grew and an awkward cough left the hero's lips. Scratching his cheek, the man looked at the ground as he asked,

"What IS your name?"

"My name?..."

a soft sigh leaves his lips, recalling the last seconds of his death. Blood from his face splattering on the ground, his little brother in front of him filled with fear and worry, the fall...

"... Uchiha Shisui."

CONCLUSION NOTE:

I'm still contemplating on whether Shisui will gain One for All or not. I already know he'll be OP since he is Shisui but ridiculously OP or not is the question. Maybe, instead of getting the punching power to destroy a city, One for All's ability will change. It could just enhance his 'Quirk' giving him the chakra capacity of a Jinchuuriki (like Kisame) and making his Sharingan unable to blind him (aka Eternal Mangekyou).

Also, here's a scene that I couldn't add in the chapter:

Knock. Knock.

Inko glanced up, half a mind still focused on the news retelling what happened earlier- the slime villain who captured Katsuki and her precious Izuku attacking the villain helplessly to save his best friend.

"Izuku? Baby? Are you home?"

Knock. Knock.

"Midoriya-san?"

She immediately stands up at the sound of a stranger calling for her from behind the door, hands brushing down her dress as she hastily rushes towards the door. Opening the door, a chain keeping it from fully opening, she sees a young officer holding a familiar looking backpack.

"Ma'am, is this the Midoriya residence?"

"Yes it is. Who are you? And why are you holding Izuku's backpack?"

"Midoriya-san, I'm sure you've seen the news. Midoriya-kun threw this at the Slime Villain and accidentally left it. One of the officers saw it as they were leaving and decided to get this back to him as thanks for what he did."

Closing the door shut, Inko slides off the chain and reopens the door, smiling gratefully at the officer.

"I'm sure Izuku would be grateful that he got his backpack back. He's been fond of it ever since I bought it. Thank you, Officer."

"No problem, Ma'am," the police officer immediately offers the bag and bows, exchanging a polite goodbye before leaving.

As the door closes once more, Inko tightens her grip on her son's bag. Izuku's unusually fond of his bag, having picked it for its color, similar to All Might's hair. He'd taken care of it since he was a kid, making sure it doesn't get destroyed, unlike his uniform, clothes, and other items. For him to forget it...

The feeling in her gut grew stronger, worry occupying her deepest senses.

Her baby boy's fine. He's just growing forgetful.

Deciding to wait for her son on the couch, she waits and waits, clock ticking by. Her green eyes grow heavy and it's not until morning of the next day that she accepts the feeling in her gut- her son is gone.