Iwaizumi - Oikawa stares for a moment, then gives the hitter/slapper a piece of his mind with subtle threats, laughs his ass off at the person for their stupidity, and lets Iwaizumi prob kick the person's ass depending who hit/slapped him. (if it's their friend group, then that's different and it's probably just joking around)
Kageyama - Oikawa stares for a little bit before stepping in to be intimidating and threatening. Unless it's Suga doing the punching, he's allowed, vice captain has privileges and he's already seen Suga smack Karasuno around so nbd.
His "student", the only one allowed to be a soulless jerk is him aside from Karasuno
daisythesorceress Cloud is a good. Though Barret can hold his own and would probably yell at Cloud, but he'd begrudgingly thank him once he'd calmed down.
๐ธSpringfallen๐ธ
Basically Oikawa is on hand to mock whoever dares punch either of my muses? Valid and welcome! He can wound their emotions while they hit back!
His "student", the only one allowed to be a soulless jerk is him aside from Karasuno