Going pro right after high school graduation is amazing. It's all Kageyama wanted. But going pro at 18 years old is a lot.
His Karasuno teammates are his best friends, but Kageyama worries that he won't be able to make any friends on the Adlers.
But there's Ushijima.
They aren't friends, they're former rivals, but Kageyama won't forget his name and doesn't have to shake his hand or make awkward small talk. The coaches know their history and take pity on Kageyama by making him room with Ushijima when they're on the road.
Which, OK, Kageyama knows him, but hours and hours with Ushijima?
What if he tries to smother Kageyama in his sleep because he's still angry about not going to nationals? (No, Kageyama tells himself, Ushijima wouldn't do that. He values me as his current setter.)
Instead, Ushijima is nice. He always invites Kageyama to things and saves him his favourite flavour of sports drink at practice. They even stay behind to work together when Kageyama asks Ushijima for pointers on spiking.
He's a nice senpai and a surprisingly good teacher.
Ushijima asks him if he'd like to travel to the next meet for the national team together. Kageyama agrees, and by now they're comfortable enough to ask each other personal questions. Ushijima asks about Hinata's Brazil planning. Kageyama asks about Tendou's college life.
Yachi almost drops her phone when she comes to one of Kageyama's games and Ushijima asks her about university. Kageyama joins him at one of Semi Eita's concerts. (Ushijima says the music is not his taste, but he likes to support his friend. Kageyama promises to keep his secret.)
The old Kageyama would be happy about their connection because it would be easier to play with Ushijima, guess his movements and that sort of thing.
The new Kageyama, the one that smiles more and laughs more, is happy to call Ushijima a friend.