4(Haikyuu)

An Au where the Youth Training Camp(Sakusa, Komori, Atsumu, Hoshiumi, Chigaya & Kageyama) group has known each other since childhood and are very close friends(plus Osamu since and Atsumu are twins...if Ushijima is part or not is up to the writer as he was part of the young training before) but no one from their teams or ex-teams know about it.

This lasts until they are all adults because despite seeing them together once or twice, everyone assumed it was a coincidence until Kageyama is forced to make a live by his manager and he forces his childhood friends to be there so they react to thirst tweets, react to edits made of them, old photos of them, talk about shared memories, etc and answer any questions(including those that come once everyone realize they have known each others for years).

I just want Kageyama to be shown to have trusted friends(outside Karasuno) and have fun with them while causing chaos as they forget to tell their other friends/teammates about being friends(and also, you can't tell me that the youth training camp group isn't chaotic).