Trust has never come easily to Kageyama.
Ever since that day, where he tossed to no one, he's shrunk into himself, trusting only himself. No one wanted his trust anyways; they just walked off the court (like them, like every single one of them) and leave him alone (on the court, in the classroom, whispers trailing behind him in the hallways): again, again. No one deserved the trust he could give, he thought to himself. It was better to keep that safe with him.
So for the rest of the year in junior high, he avoided people. He was a setter, after all, not a foolish, naive child. Setters could serve, and spike, and play volleyball even without using other people. The other six just save the ball from hitting the ground; he could do all the work. They should be grateful that someone could do all the work for them, he thinks.
The lazy, weak-willed people that others called a 'team'—he knows better than that.
Sometimes, when he was home, he'd set the ball to himself on his bed, reassured by the feeling of the leather against his finger pads, the weight pressing into his hands as he flicked it up again. Set, receive. Set, receive. Sometimes, he'd pretend that the one setting and the one receiving were different people: he'd be setting the ball to someone who could match him, who could challenge him to set faster, stronger.
(He'd imagine this as he practiced in the gym, without his worthless team, whacking the ball across the net to slam down on the other side. Always a perfect hit. No one would see it.)
And he decides, in the end, that Karasuno will be decent enough in improving his volleyball skills. God knows how long they've been starved for a win.
The one thing he doesn't decide is Hinata.
Their first meeting is...not pleasant. Rather, it should be a reunion of sorts, although Kageyama only vaguely remembers the spitfire redhead, from that one match last year. An easy match, with weak players, he tells the boy.
The fight only ends when they're thrown out of the club, applications with them. He blames Hinata, Hinata blames him, but with no other choice, Kageyama decides to work with the idiot to get back in.
And as frustrated as he is with the situation, he feels a grudging admiration when the boy declares the state of his makeshift training. His determination, too bright and fierce to contain, spurs Kageyama on to prep for the practice match. (It helps that Hinata's got some sort of bite along with all his bark.)
There's no way he could've prepared for the lightning-quick spike they do.
There was not even a chance that Kageyama would expect Hinata to trust him. Close his eyes and reach for the ball he wouldn't see coming.
But he does. And the fiery little redhead suddenly becomes so much more for Kageyama.
They win that match. The team loses to Nekoma. Karasuno wins too many to count, and loses enough to count on two hands. Not bad for volleyball.
Trust. Once, an arrogant boy trusted only himself, and set the ball to no one on the court. Once, a boy trusted only himself, and ended alone when he needed people the most.
And once, the boy who trusted only himself found another who would trust him. Mutually, unbreakably. Forever.
Kageyama trusts Hinata now. Whatever they're doing, whichever match they're fighting together, he trusts that the redhead will give it his all. He always does.
Hinata confesses first, his cheeks as red as his hair as he stammers out his feelings. Kageyama has the first kiss, a quick peck on the lips as an answer to Hinata's confession. And their first public reveal turns out to be sort of useless, as everyone on the team assumed there was something going on all along.
Kageyama doesn't mind. He trusts that there's plenty of other firsts to come.