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"Before I start training you, Yukio, I need to tell you something important," Father Fujimoto said, sitting behind the teacher's desk in an abandoned Cram School classroom. "Something you can't tell anyone, not even Rin. Especially not Rin."
Yukio's eyes widened; he knew that his Exorcist training was to be kept secret from Rin, but he had no idea what this new secret could possibly be. Still, Yukio nodded solemnly. "Father... What is this secret about?"
"It's about your birth parents," Father Fujimoto said with a quiet, sad sigh, massaging his temples. "I hoped I could wait until you were older to tell you this, to tell you and Rin at the same time... But it's important that you know this if you want to be an exorcist and properly protect your brother."
"Our— Our birth parents?" Yukio said, looking stunned; his father had never said anything about Rin and Yukio's parentage or how they'd come into his care aside from outlandish stories designed to simply keep them occupied. "You know who they were?" Why would their parentage be important to know as an Exorcist? Unless—
No, they couldn't possibly have a demonic parent. Sure, Rin was unnaturally strong and angry, but he was human. They'd both taken Communion and touched holy water without issue, so that couldn't possibly be the issue. Right?
"Of course I know who they are. In fact, I knew your mother personally," he said, offering the smallest of smiles and no other information. "I can't say I ever met your birth father, thank goodness."
Thank goodness? Their birth father must be someone— or something —horrible... Maybe he was a drug lord. Or a notorious gangster. That would explain Rin's delinquent attitude. "Who— what —is he that makes him so horrible?" Yukio asked with the stare of a terrified deer caught in the headlights. Father Fujimoto's eyes softened, saddened by the coming loss of innocence.
"Yukio... You and your brother are the offspring of a human woman and a demon," Fujimoto continued solemnly, adjusting his red-tinted glasses. "And not just any demon, either... You two are the children of Satan."
Suddenly, Yukio couldn't breathe; he instinctively reached for the inhaler that he usually kept in his pocket despite knowing that this was not an asthma attack. To be not only the spawn of a demon, but the spawn of Satan... "It's not possible," he gasped, horrified and in denial. "Rin and I, we're... we're both completely human..." A small voice in the back of his head whispered about Rin's rages and strength, but he tried to push it out of his mind.
"You're human," Fujimoto said with a small sigh. "You were lucky enough to be born too weak to inherit anything demonic. Rin, on the other hand, was born with everything— claws, pointed ears, fangs, a tail, and Satan's flames. We sealed them away when he was moments old so that he could lead a somewhat normal life. The seal can't hold forever, though; the power your brother inherited is too strong to be held back by even the strongest seals. By the time you both are fifteen, his powers will start manifesting... You need to know so that you can help him when that starts happening."
Yukio wasn't even listening to anything his father had said beyond Satan's flames; how could his beloved brother, his Nii-san who had always protected him, be a demon? Yukio tried to imagine his brother with a tail, pointed ears, and fangs, like his father had said, and he couldn't. That wasn't Rin. That couldn't be Rin. Rin couldn't be the same thing as the beings that had tormented Yukio for as long as he could remember. Despite his best attempts to keep it in and appear strong, Yukio began to weep. "Nii-s-san can't be a demon... H-he c-can't, he's too n-nice," the young boy sobbed. He began to feel a deep, intense hate for the blood coursing thorugh the veins of him and his brother. He hated their very DNA. Why did they exist?
"Yukio," Father Fujimoto murmured, gathering the seven-year-old into his arms. His voice was warm and comforting, the same tone he used when the twins needed reassuring about bullies or nightmares. "This doesn't change anything about you or Rin. If it did, I wouldn't have taken you in, now would I?" Yukio shook his head, rubbing at his eyes. Fujimoto gave him a smile, nonverbally saying 'atta boy'. "Rin's still the same boy he is before you knew this— and even if he looked like a demon, he's still very human on the inside," the priest reassured his adoptive son. "You two are more human than a lot of full-blooded humans I've met, actually. So I don't want you thinking about yourself or Rin different because of this, okay?"
"O-Okay," Yukio promised tentatively, not sure if he'd be able to follow his father's wishes. How could he not think different about himself and his brother now that he knew they were the children of the worst monster to ever exist? Yukio still couldn't get the image of his brother as a demon out of his head.
Once they'd gotten home, Yukio had been unable to even glance at Rin's face during all of dinner and bedtime. Rin seemed to be concerned by the sound of his voice, but it was simply impossible for Yukio to even try to act normal knowing what he knew. Every time he saw those bright blue eyes, Yukio could only see the blue flames of Satan Rin had inherited. Yukio was afraid that if he looked at his brother or made eye contact right now, he'd completely lose it. Rin kept asking him what was wrong, which was making it even worse— Yukio felt horrible about the hatred bubbling up in his chest because of something Rin didn't even know he was. Nii-san was so nice, and he tried so hard to be a good person despite everyone calling him a demon; what would happen if he found out he really was a demon? Rin would probably be heartbroken, but that didn't stop Yukio from utterly loathing what his brother was deep inside. His Nii-san, the one he'd admired since birth, was a monster and didn't even realize it. It angered Yukio that the monstrous one was being protected and coddled while he, the human child with a chance at a normal life, had to shoulder the burden of this secret for the both of them.
Yukio told his brother that he had a bad stomachache and went to bed without even brushing his teeth.
His dreams that night were vivid and horrifying, like most of his nightmares usually were. His father was taking Yukio out on his first mission, and the young boy was nervous but excited. Father Fujimoto explained that there was a demon causing trouble at Rin and Yukio's school, and that they had to go get rid of it.
The second they arrived at their school, though, Yukio knew something was horribly wrong. Desks were upside down as if they'd been toppled and thrown, blue flames were licking at the floor, and the kids who bullied Yukio all the time were cowering in a corner. In another corner, the demon responsible was standing facing the wall, making it impossible to identify.
This didn't look like a demon attack, Yukio thought to himself— this looked like what Rin did…
As if on cue, the demon turned around, revealing that he was Rin— but at the same time, he wasn't. Instead of his usual warm smile, this Rin's grin was sharp-toothed and maniacal; his ears were much longer and pointed, as were his nails. Behind him, something that looked like a furry whip— a tail, a voice in Yukio’s head said—waved.
"What's wrong, otouto?" Rin said, his voice exactly the same as it normally was and yet wrong. Rin never called Yukio 'otouto', never had that sly grin on his face while he did anything. Especially not when talking to his beloved baby brother. "I'm still your Nii-san. You love your Nii-san, don't you?"
“You’re not my brother! My brother isn’t a demon!” Yukio shouted, spitting the word ‘demon’ out like it was a derogatory term. The young Exorcist-to-be took a gun out of a holster resting on his hip that he wasn’t sure how he got, pointing it at his brother— no, at the demon —with shaking hands. An odd look came across the demon’s face for a moment before it was replaced by a sharp grin.
“Didn’t Tousan tell you what I was? What, you thought I’d stay human forever? I thought you were the smart one, but you’re even dumber than I am,” the demon sneered, baring large, sharp fangs at his younger brother. "This is what I really am, otouto, so you better get used to it!"
Yukio's eyes snapped open, his breathing heavy and his sheets drenched with sweat; he had nightmares often, but none like this. He tried to keep quiet in order to not wake his brother, but it was too late— Yukio could hear someone walk over to him, and turned to see a blurry form that he knew was his brother.
"Yukio? Are you oka—" Was all Rin could get out as he reached out towards his younger brother before his hand was smacked away, a fearful look on his baby brother's face that he hoped he'd never see directed at him.
"Leave me alone!" Yukio snapped, his tone surprisingly sharp and his eyes livid. The fact that he could make out that Rin felt hurt despite his horrid vision gave the young boy pause, but he quickly pushed down any regret he might have felt at pushing his brother away. Rin might not have known it, might have thought he was doing good, but he was a demon. Even if he didn't mean to, he'd hurt Yukio in the end, just like Yukio’d seen him hurt other people. Just like Yukio had seen other demons hurt people. “Just… Just leave me alone right now, Nii-san,” he muttered, ducking his head and curling in on himself.
Rin frowned, staring down at his feet and tugging at the hem of his shirt. “I jus’ wanted to help,” he mumbled, clearly hurt. Seeing Yukio, the one person Rin had always counted on to never be afraid of him, cowering away from his made his chest hurt and his eyes sting with tears. He’d really thought Yukio knew that Rin would never, ever hurt him.
“I know,” Yukio replied, voice softening slightly. The young boy sighed, turning over in his bed so that he wouldn’t have to see how upset his older brother was. “I’m fine, alright? Go back to sleep, Nii-san.”
“If you say so,” Rin said, reluctantly shuffling back to his bed.