A/N: Sometimes I feel like writing Naoya backstory. As such, this is 90% headcanon, down to the main character's names and family and their relationships, and how the events leading to Naoya entering their household went down.
Main character name is Keiichi Kimura, just like in the rest of my fanfiction.
From the moment he met the child, it was obvious to Naoya who he was. It was written all over the toddler's face, etched into his eyes and radiating out from his innocent smile. It was in the way he clutched a ragged stuffed sheep close to him and pulled his mother's skirt close as he stared up at this person he'd never met before.
"Say hello to your cousin, Keiichi!" his mother urged, and the boy tentatively stepped out from behind her. Without looking up at Naoya, he said, "'ello," and scurried back behind her. Naoya's parents chuckled.
"Gosh, he's gotten so big. Last I saw him he was the size of a bean."
"I wouldn't call him that small. Don't let how shy he's being fool you, though. He's a little homewrecker. I can't put him to bed without him fighting me all night long."
"Oh, is that where that bruise on your forehead came from?"
Perhaps it had been fate that handed Naoya this opportunity, giving him a child so young. It was just asking for him to reach out, seize this fragment, and nurture it into a perfect little devil. A part of him, the more impulsive part that he had to work so hard to tame when he was at this age, told him to just grab Keiichi's wrist and run off. But no. There were other ways to go about this. He had to be patient.
"So how old is he, Kenta?"
"He just turned three last month!"
"Ahh, our Nao-chan's ten now. You wouldn't know it from how tall he's growing, though. And he spends all his time cooped up in his room on his computer, like a moody teenager…"
Naoya's cold gaze remained on Keiichi. The boy put his finger in his mouth and sucked on it.
"Don't do that," Naoya stated, and the boy quickly whipped his finger out. "You'll cause your teeth to grow in badly."
"I've already got all my teef," Keiichi said, and opened his mouth to show. He indeed had a full mouth of baby teeth.
"I don't care. You still shouldn't do it." Naoya scoffed. His father chuckled.
"Trying to be the cool big brother, Naoya?"
"No," Naoya stated automatically, though he could help but feel a twinge of pride at that question. He stepped behind his mother, carefully moving so that he didn't even brush up against her, and said, "Can we leave?" He was sick of standing there, unable to do anything, while that boy stared at him with his innocent eyes. It made him want to vomit.
"No, Naoya, we still haven't met with your grandparents…"
No one could have seen that terrible accident coming. It had been an entirely unlikely set of circumstances all coming together with horribly fatal results. How could anyone have known that the streetlights on that particular intersection would malfunction during the middle of rush hour on that foggy day? And when the lights all said "go" and no one could see each other through the thick fog, there was nothing to stop those cars from all smashing into each other. Among the dead were Kouta and Eiko Kimura. The couple was survived by their son, Naoya, who had been home at the time. It was only later that someone checked the computer systems controlling the lights and found evidence that someone had hacked into it, and by then it was far too late.
The funeral was a few days later, and a small army of family members, including Kenta and Mizuki Kimura, showed up to mourn. Naoya did not speak for the entire ceremony, instead keeping a stoic look on his face and avoiding eye contact whenever possible. As far as anyone could tell, he was in shock, and so they felt fit to leave him be.
"Someone's going to have to take care of him," Naoya's grandfather, the eldest member of the Kimura family, said to Kenta after the funeral was over. "I've already spoken with Eiko's family, and they won't do it. He bothers them."
"Bothers them? Bothers them how?" Kenta asked, but Naoya's grandfather just shook his head, so Kenta continued. "You won't take him?"
"Your mother and I are both getting up in our years. We won't be able to be good guardians for him. It's best if someone younger and stronger takes care of him."
"Mizuki and I both work long hours, though. We can't hire someone to watch both Naoya and Keiichi," Kenta said.
"Then get the kid to watch your kid! He's old enough to stay home on his own, and it'll save you some money on the long run. Besides, you owe your brother, don't you?"
"I'll talk to Mizuki about it," Kenta said evasively.
But by the end of the funeral, it had been decided that there was no other option, and Naoya went along with his cousin's family, just as he had planned.
Moving Naoya into Keiichi's house had been a pretty simple matter. All he'd asked they bring from his house was a desktop computer and his clothing, both of which he'd managed to move into Keiichi's room fairly easily. The small blue-haired toddler had watched transfixed as the boxes were carried in before finally turning to his mother and asking, "Why's he here?"
"Your cousin Naoya will be living with us for now on," she answered. Keiichi's eyebrows drooped and he stuck his finger in his mouth.
"In here?" he asked. Naoya gave him a stare. What he was about to say felt incredibly foolish, yet somehow it felt right.
"You can think of me as your big brother. I won't even mind if you call me 'oniichan'," he said.
"Niichan…" the boy rolled the words on his tongue a couple times, testing it out with different inflections every time. "Niichan… Nii… chan."
It was positively adorable. For the first time, Keiichi stepped out from behind his mother's legs, still clutching his abhorrent sheep doll and keeping a finger in his mouth. Naoya walked over to him, casually pulled Keiichi's hand out of his mouth, and ruffled his hair. The boy gave a small protesting moan before retreating behind his mother's legs again.
Slowly, Naoya lowered his hand. That innocent way that Keiichi moved, even in the way he stayed so close to his mother. It reeked of the essence inside him, and it made Naoya feel like vomiting. He couldn't let himself always be reminded of his brother, even with all of Keiichi's unknowing similarities, but the boy made it so difficult for him. He wouldn't be able to do it in this incarnation, he could already tell. All he'd end up doing was killing him again. Even now, when everything was in his grasp, he…
And suddenly, he found a small hand grasping one of his fingers. He looked down at the boy, who was now staring up at him, his wide eyes welling up with tears.
"I'm sorry, Niichan," Keiichi said, tugging on Naoya's finger. "I didn't mean to make you mad."
Ah. So his expression had shown through. He was normally better than that at hiding his true thoughts. He ruffled the boy's hair again. "You shouldn't worry about me." He pulled his hand out of Keiichi's and began to walk toward his room, and a hand seized his wrist. He was not surprised to see that it was Keiichi's hand. "Leave me."
"No! Not until you're happy!" Keiichi said, and he began to pout. Naoya's mouth curled into a wide smile.
"But Keiichi. I am smiling. See?"
"No!" Keiichi pulled Naoya back, and now he was beginning to feel frustrated. Just how stubborn was this kid? "You're not happy at all!"
"Then what must I do to convince you that I am?" Naoya asked.
"You should…" Keiichi yawned, and he rubbed at his eyes. "You should…" Naoya could see the signs of a sleepy, cranky toddler, so he reached down and picked him up.
"I'll tell you what, my precious little brother. Why don't you tell me after you've had a good nap, hm?" he said. Keiichi didn't hear, as he was already asleep against Naoya's shoulder, quietly drooling into his shirt.
Naoya carried Keiichi to his bed and laid him to sleep. The boy was already attaching himself to him. That much was obvious. Maybe he shouldn't count himself out in this life quite yet, not when he'd taken so many steps to get himself close to the boy. Even if he did let himself become so attached, what did it matter, when everything had been handed to him like this? The next few years would be very interesting…