Kadota has known Izaya since elementary school, except not really. They were never in the same class and Izaya was never particularly close friends with anyone. He was smart and friendly and personable at a glance, but it was all surface gloss. A shiny little shell of a nice average boy that nobody really knew and sometimes Kadota wonders if he was as hollow inside then as he seems to be now.
Not that Kadota thought about such things at the time. He was like everyone else, he had his own friends and concerns and as such he never really noticed Izaya until Izaya wanted to be noticed. It's only years later when he lays everything out in his mind and goes over it slowly that the fact that Izaya has always been a bit odd comes into focus. Long before those disastrous high school years, even long before middle school and that summer break in first year that ended with everyone whispering behind their hands about how Orihara-kun stabbed his friend. Right from the start Izaya has simply been strange and distant. He was just better at pretending back then. Or maybe he just cared more about pretending and camouflaging and being thought of as normal.
Whatever the reason it isn't until high school that Kadota can say that he knows Izaya, and then it's only because Izaya takes a peculiar sort of interest in him. As much as Izaya likes to say that he loves to watch people what he really loves best are the oddities. The ones that are a little harder to predict and manipulate and don't succumb so easily to all those little nudges he gives. It's why he's friends with Shinra (as much as it can be said that Izaya is friends with anyone), it's why he torments Shizuo so much.
And it's why he starts hanging around Kadota. Because as average as Kadota may be, he's also odd in the sense that he doesn't quite move the way Izaya wants him to. Kadota is exceptional at keeping himself out of things and trying to tug him in is one of those side games Izaya plays when he feels like a change of pace from his usual grand schemes.
"You're my hobby, Dotachin," Izaya says one afternoon when Kadota tells him for what feels like the thousandth time that he doesn't particularly care about whatever Izaya is currently plotting and to leave him out of his manipulative bullshit. "There's no such thing as a true neutral, yet that's what you're trying to be. And I'm going to prove that you can't."
"I have no idea what you're talking about. Why do you have such a hard time grasping the fact that I'm just not interested in these stupid games of yours?"
"But the thing about games is that everyone has to pick a side. You can't just keep sitting out and say you're not playing. That's no fun at all. Even if you're on a side all to yourself that's still a side..."
"Fine, that's the side I'm on. Go away."
"But you're still sitting out." Izaya is perched on a table in the library. Idly kicking his feet and watching Kadota browse the nearby stacks. "And that's not how you play."
"If I'm on a side all to myself like you say, who says I have to follow your rules. You're just like a sulky kid, making up new rules as you go along because you hate losing."
"That's how the game works."
"No, that's poor sportsmanship. Go away, Izaya-kun."
Izaya makes a face but he does go away, for that afternoon at least. Ultimately Izaya never goes away for long so all Kadota can do is take the reprieves when he can get them.
After a while Izaya stops badgering him about sitting out, although he never stops regaling Kadota with detailed explanations of all his plans and plots. Complicated machinations that only become more and more horrible as the weeks slowly turn into months and Kadota barely makes a token effort to tell Izaya not to involve him with such things anymore.
Sometimes he wonders if it makes him as bad as Izaya is. Maybe it makes him worse somehow that he can quietly listen and not lecture Izaya about how he shouldn't be doing these things. Or run off and tell someone about what Izaya is up to.
Except doing any of those things would make no difference one way or the other. Izaya doesn't listen to lectures (he's watched Shinra try and fail to be Izaya's conscience on more than one occasion) and most people already know that Izaya is behind the worst things that tend to happen at Raijin high school. The ones that don't are the ones tangled up so tight in Izaya's various threads that nothing anyone says will ever change their minds.
He doesn't want anything to do with Izaya's games, but if he has to play then it will be by his personal rules that keep him as far away from whatever Izaya is up to as possible, even if Izaya won't quite let him be.