Warnings: graphic illness, swearing, sadness

The episodes started when he was ten. Rin remembered waking up with a pounding headache and an overwhelming wave of nausea crashing into him. He scrambled out of bed, hitting the floor and rushing to the bathroom, Yukio's sleepy, confused calls following him. He clasped a hand over his mouth, tears building in his eyes as vomit pushed up his throat and out of his mouth before he made it to the toilet. The liquid dripped onto the floor as Rin desperately cupped his hands to hold the vomit. His knees hit the floor as he reached his destination, his hands releasing the pungent vomit into the toilet. His hands felt gross and sticky, and his head lurched over the water as another round of sickness hit him.

"Rin?" Shirou's concerned voice came from the bathroom door. His only answer was the sound of Rin's violent puking. Shirou pushed the door open, took one look at the ill boy, and kneeled next to him while rubbing his back. "You're definitely staying home in bed today," Shirou announced, frowning worriedly at the new development. Rin's answering moan offered no resistance.

"Do you want me to stay?" Shirou asked after Rin stopped throwing up for a moment. The boy was pale and shaky, but he still shook his head. "All right," Shirou conceded. "I'll check up on you in a minute. I'll be back with your medicine, okay?" Rin nodded and gripped the toilet seat tightly, staring down at the contaminated water.

"Is Nii-san okay?" Yukio hovered at the door anxiously, flinching when he heard Rin heave behind the door.

Shirou paused, then answered, "He's very sick today. I'll write him a note, so would you mind giving it to your teacher for me, Yukio?"

Yukio agreed although he was obviously distracted by the thought of his sick twin. By the time Yukio left, Rin was tucked back into bed while Shirou talked in a low voice outside his bedroom door. Drowsily, Rin watched his father hang up the phone and stare at his clenched fists. As his eyes drifted shut, he was completely unaware of how often he would have to stay home from school in the future.

*...f...*

It was a few years later that Yukio started asking questions.

"What's wrong with Nii-san?" Shirou shifted his feet nervously as his youngest son stared him down, arms crossed. He'd been cornered by the preteen before he could escape the (admittedly understandable) protective twin.

"The doctors said he's just more susceptible to colds," he answered reassuringly, placing a hand on Yukio's shoulder. Yukio was decidedly unimpressed.

"What kind of cold keeps someone bedridden for days?" he demanded.

Shirou sighed, rubbing the bridge of his nose. "Rin's body is...weak," he admitted. "Dr. Yashino hasn't found anything conclusive yet." A wave of guilt hit him as Yukio's face crumpled in worry.

"Could it be related to...our biological father?" Yukio asked, although his shoulders had already slumped in defeat.

Shirou shook his head. "I'm sorry, Yukio. If anything, his bloodline should have made his immune system stronger." Exhaustion weighed down on his shoulders as he thought of sweaty, pale, and shaking Rin a few hours ago. Over the past two years, Rin's condition had only worsened. At his last checkup, Rin's doctor had warned him of probable approaching symptoms - for instance, blood in his vomit. It was bad enough having to witness Rin dry heave; just thinking of him being in more pain caused Shirou's heart to clench anxiously.

Shirou was saved from answering any more questions when Rin entered the room. "Hey, Yukio, have you seen my sketchbook?" Rin asked.

Yukio turned to his twin, plastering on a smile. "Did you check the kitchen?"

"Oh, I didn't!" Rin beamed. "You're like a mom, Yukio; you always know where everything is." The tension in Yukio's body slipped away at Rin's casual, ridiculous comparison.

"I am not," Yukio denied, pink creeping up his cheeks. "If anything, you're the mom! You're always cooking and cleaning!"

Rin wavered. "Well, maybe neither of us is a mom," he suggested. Shirou snorted at the compromise.

"Speaking of cooking, what are you planning on dishing out today, Rin?" Shirou asked, ruffling his eldest child's hair.

Rin grinned up at him. "Sukiyaki!"

"Are you sure you should be cooking already?" Yukio hovered over Rin anxiously as Rin started pulling his family towards the dinner table. "You were throwing up again this morning..."

"I'm fine!" Rin insisted. "I feel great!"

Yukio frowned. "Are you sure-"

"Is Yukio being a worrywart again, Rin?" One of the clergymen teased as the three entered the room. Yukio sniffed.

"I am not being a worrywart," he began hotly, clearly about to preach the importance of Rin taking care of his health. While Shirou could wholeheartedly agree with Yukio's concern, sometimes the boy went a bit overboard.

"He's only kidding, Yukio," Shirou said gently, patting Yukio on the back as the group of clergymen laughed.

"Seriously, Yukio, I'm okay," Rin said, smiling warmly. Yukio sighed, reluctantly smiling back.

"If you say so, Nii-san...but if you start feeling sick again, you have to promise to go lay down!"

"Yes, Mom," Rin saluted, earning an irritated, half-hearted glare from Yukio. The priests snickered as Rin quickly darted into the kitchen before he received a lecture from his brother.

"You two sure are growing up fast," Daichi, a middle-aged exorcist with graying hair, said fondly, distracting Yukio from his sulking. "I remember when you were both little tykes. You were always clutching Rin's sleeve while he tried to find the most dangerous situation possible."

"Remember the first time Rin tried to make chicken soup for Yukio when he caught the flu?" another piped up, and everyone burst out laughing at the grimace that flashed over Yukio's face.

"In Rin's defense, he had only just started learning how to cook," Shirou chuckled, remembering the burnt, sticky soup that was more solid than liquid.

The group continued to reminisce and joke boisterously, and Yukio began to drown out the laughter and work on his homework instead. An hour passed by, and Yukio's stomach started to growl incessantly for a bite of food.

"How much longer until dinner is ready?" Yukio asked, gaining Shirou's attention.

"Don't know," Shirou answered, blinking in surprise when he noticed how quickly the time had passed. "Oi! Rin! Should we start setting the table or what?"

There was no answer.

"Rin?" Shirou called again, urgency coating his voice. The clergymen quieted.

Shirou quickly stood up, surging forward to the kitchen door and pushing it open. A pot of water bubbled loudly, and the cutting board contained a row of sliced sirloin, a knife resting off to the side. The vegetables, however, sat next to the sink, glistening with drops of water after being washed. Shirou's eyes drifted down.

Sprawled across the floor, unconscious and ashen-faced, was Rin. His cheek was bright red, a telltale sign that a bruise would be forming, and his body was jerking and twitching like a puppet on a string. Shirou inhaled sharply, barking, "Call 119!" as he rushed to Rin's side. There was a flurry of panicked movement as everyone scrambled for a phone. Shirou glanced up to see Yukio's terrified expression before he focused back on Rin. His son's head lolled to the side, eyes opening blearily.

"Rin?" Shirou said softly. "Can you hear me?"

Rin stared at him with dilated pupils for a moment, blinking unnaturally. He opened his mouth, a nonsensical noise escaping as a line of saliva trailed down his chin.

"Da...?" he slurred, shuddering. Shirou's heart broke.

"I'm right here," he said, trying to mask the shakiness in his voice. "You're going to be fine. The ambulance is on the way."

Speak of the devil - a group of paramedics pushed their way through the crowd, shouting orders and looking far too professional in the face of a sick child. Rin's eyes followed the new arrivals for a few moments before they drifted back shut in exhaustion.

"Excuse me, sir, you'll have to back up a little," a woman said firmly. Shirou stood back as the team checked Rin's vitals before lifting him up on a gurney. Yukio reached out for Shirou's hand, and Shirou grasped it tightly.

"How long has he been like this?" A man with a clipboard placed a hand on Shirou's shoulder sympathetically, but Shirou was too numb to express any gratitude.

"I- I don't know," Shirou admitted shamefully. "Rin likes to cook without any distractions, so he was in there for about an hour before we noticed that something was wrong."

"What happened to him?" Yukio asked fearfully.

"Looks like a seizure," the medic said bluntly, although his tone wasn't unkind. The man turned to address Shirou directly. "We'll need his medical history on the way to the hospital." He hesitated, glancing down at the ironclad grip Yukio had on Shirou. "Only one person is allowed in the ambulance with him."

Shirou nodded robotically. He murmured a goodbye to Yukio, hugging him tightly, before following the paramedic into the back of the ambulance. Distantly, he could hear one of the priests reassuring Yukio that Rin was going to be okay.

Looking at Rin's pale, sunken face, he wondered if his son would ever be okay again.

*...f...*

"I don't want to tell him," Rin said stubbornly. Shirou groaned. This wasn't the first time they had argued over the matter of telling Yukio the extent of Rin's illness, and he was sure it wouldn't be the last.

"Rin, he has to know," Shirou persuaded insistently. "Yukio is going off to high school soon - he already knows that something is wrong. If anything happens while he's away, it will be even more of a blow to him when he finds out the truth."

"If we tell him now, he'll just do something stupid!" Rin argued. "Knowing him, he'd probably try to quit high school so he can stay home with me. I don't want him to give up on his future just because I don't have one!"

The stricken look on Shirou's face told Rin he had gone too far. Too proud to apologize for his words, he announced, "I'm going for a walk," stomping away and slamming the door shut behind him. He muttered angrily under his breath as he stormed around the corner, wandering aimlessly. Before long, he ended up in a shabbier part of town, broken windows and graffiti gracing every building. He felt his previously boiling anger cool with every step he took, the cool spring air never failing to calm his rampant emotions.

His moment of peace was destroyed when he came across a bunch of wanna-be thugs torturing defenseless birds. He swore he could almost feel his head explode in fury as he approached the group.

"Hey! You! What the fuck do you think you're doing?" Rin yelled, kicking the metal gate hard enough that it rattled loudly against the cruel laughter of the teenagers.

The laughing stopped.

"Who're you?" The leader looked him up and down, sneering. Rin took a moment to size the other up as well; he had some muscle, but nothing prominent, and although he wasn't the best-looking person Rin had ever seen, he was far from unattractive. He had a moment of war flashbacks from when he was thirteen and wanted facial piercings because they were "cool." He had spent hours looking up all kinds of different piercings, and he had especially wanted a few that rested on his cheekbones. The sunlight glinted off of the balls of metal poking out from the gang leader's forehead, and Rin spared a second to fervently thank Yukio, the old man, and God for not going through with his "passion."

"I'm the guy who's going to kick your ass if you don't stop what you're doing," Rin scowled, glaring ferociously. The leader snickered, and his minions echoed him stupidly.

"You?" He eyed Rin's worn-out face and pale features. He took a step closer. "What are you going to..." He trailed off, an odd expression overcoming his face. Rin forced himself not to step back when the guy stood in front of him and sniffed the air deeply.

"Boss?" The minions shifted on their feet uneasily. Rin struggled not to do the same. The leader was frowning, now, looking at Rin with a dawning epiphany.

"You're..." Horror, shock, and reverence flashed across his face. "My Prince, Lord Satan will be pleased to have finally found you! Please, we must depart at once!"

This time, Rin did take a step back. He gaped. "Wha?" The minions seemed to have the same reaction judging by their disbelief.

The teenager reached out, grasping his hands, nails biting into Rin's skin. Rin's vision distorted, black creeping in the corners of his eyes as suddenly hundreds of floating creatures bumbled through the air. He choked when giant horns curled up from the leader's head, skin darkening and eyes flashing red.

"Demon!" a familiar voice cried out from behind him. Rin whipped his head around, slumping in relief when he recognized Shirou. The old man was clutching his cross, muttering under his breath with the skill only a priest could have. As the demon screeched in pain, skin hissing and steaming, Shirou grabbed Rin's arm, pulling him close. "We must hurry," he murmured, walking briskly back to the monastery. Rin barely noticed as the now-human boy collapsed to the ground, his friends scrambling as far away as possible from him.

"What's going on?!" Rin's voice broke. Shirou forged forward.

"There isn't much time. Rin, your birth father- it's Satan." Shirou slams open the doors to the monastery, barking orders while giving Rin a rundown of the situation. Rin could barely manage to understand through his dumbfounded stupor. He yanked his arm away from Shirou, forcing them to stop in their tracks.

"Why didn't you tell me?" Rin whispered, feeling betrayed.

Shirou hesitated, struggling to decide whether to answer or get Rin to safety. "I was hoping you would never need to know."

Shirou's explanation was too lacking, too simple, and too convenient for Rin to believe. Rin took his adopted father's claim and morphed it into something dark. "You were hoping I would die before something like this happened."

Shirou's face crumpled. "Rin-"

"Were you secretly happy when you found out I was sick?" By now, all movement had stopped, the rest of the clergymen staring at Rin's outburst with wide eyes. They inched their way out of the room with impressive stealth. "I bet you were relieved that you wouldn't have to deal with me - the son of Satan! What about Yukio? Did he inherit Satan's power?" A fizz of electricity sparked in the air.

Shirou could only shake his head in distressed denial. Rin laughed coldly. "Well, isn't that lucky! Guess it's fate that the demon ended up sick!"

"Rin, please-" Shirou pleaded.

"Did Yukio know about Satan?" Rin demanded. Shirou didn't respond, but the guilty expression said everything. Rin went from angry to heartbroken in seconds. "You didn't trust me. Was I even a son to you?"

Shirou flinched violently. "Of course you are! Rin, I promise you, I only ever thought of your safety! I wanted you to live a happy life without you ever having to worry about any of this."

Rin stared down at his shoes, breathing harshly. Tears threatened to drip onto the floor. "I hate you," he whispered. Time seemed to stop.

Blue flames erupted from Shirou's body, ears lengthening and fanged teeth sprouting. He muttered something alien, and a golden gate appeared, elegantly carved and cursed with horrendous images. Something dark and disgusting oozed from the passage, body parts stuck in an inescapable sludge. Rin could feel the heat of fire licking his skin eagerly as a twisted laugh echoed through the room. "Well, well, well, who do we have here? My very own son! You've grown up so much- you're all ready to come home."

Rin jerked away from the outstretched arms. "I'm not your son!" he said, but it came out shaky and streaked in dread. A series of hacking coughs overtook Rin, leaving him unsteady and feeling weak.

"Now, now, I know you're going through your teenage rebellion phase, but it's time for you to come home. I've missed you dearly, you know." Blood dripped from Shirou's eyes, but that was apparently no hindrance to Satan when he lunged at Rin, dragging him kicking and screaming to the portal. "It's time for you to take your proper place, my son! You will be reborn into a King of Gehenna! No longer will you be restricted by your human nature; it is an event to celebrate!"

A horrible grin contorted Shirou's face in triumph as they reached the portal, but then it faltered as the red suddenly faded from his eyes.

"This boy is my son! And I won't let you have him!" Shirou ripped his blade from his side, aiming it directly for his stomach. The squelch of guts sickened Rin to his core, and he desperately clutched his father as the blue flames dwindled. His eyes strayed towards Kurikara, and with a burst of determination, he pulled off the sword's cover. He focused on Shirou and said, "You can't die on me yet!"

As the twang of metal reverberated against the sheath, Rin felt peaceful. The fire that washed over him was cool to the touch, and for once, he did not feel the overwhelming fatigue that had dominated his body for half of his life. He felt good - really, really good. He gripped the sword with a startling amount of strength and firmness, exhaling. Then, he struck the blade through the sludge, encasing the room with cyan flames, and everything went black.

lol. y'all are too good to me. since u guys r so nice i thought "why don't i make the fight between shirou and rin 10x as sad as it was originally" and here we are. ily. thanks for sticking with me. i promise updates will come sooner - this year has sucked.