Honestly, the dynamic writes itself, doesn't it? You’ve got the whole ‘fated rivals, best enemies’ foundation from 'Kuroko’s Basketball' baked right in, so most fics just lean into the obvious: the arrogant, genius loner (Aomine) and the brilliant, attention-seeking copycat (Kise) who’s the only one who can genuinely challenge him. A huge chunk of stories are post-canon, exploring that ‘now what?’ after the Winter Cup. They’re pros, they’re on different teams, the public rivalry is a media circus—but who else truly gets the pressure they’re under? It’s that isolation-that-only-the-other-understands trope cranked to eleven.
A lot of authors love playing with Kise’s modeling career too. It becomes this great source of conflict or pining. Aomine sees him on a billboard or in a magazine spread and gets hit with this confusing mix of pride and possessiveness. Is he annoyed because Kise’s everywhere, or because he wishes he was the only one who got to see him like that? The fics that dig into Aomine’s jealousy, especially when it’s quiet and simmering rather than explosive, always feel the most in-character to me. He’s not the type to confess easily, so you get a lot of that delicious, frustrated yearning from his POV.
The established relationship fics often revolve around secrecy—hiding it from their teams, from the public, from their old friends. It creates this intense, private world just for the two of them, which fits their bond perfectly. You also see a fair amount of injury/comfort, where one gets hurt (usually Kise, pushing his body too far) and the other has to confront the idea of losing him, not just as a rival but as… everything else. It’s a solid way to force feelings to the surface. The fluff tends to be competitive even in downtime, like stupid video game matches or cooking competitions that end with a mess in the kitchen. It never really stops being a battle, just a friendlier one.