Rei is always going to be a prick no matter what. Even if it wasn't his true personality, on the outside he is nothing but a teaser and to say the least, full of himself. He also had a lot of social leverage.

One afternoon, after school had ended Rosho(you) was greeted by a knock on his classroom door. He shouted for the person to come in but was very stunned, and a little annoyed to be greeted by Rei. Sure, they were both part of Dotsuitare Hompo but that had nothing to do with why he ws at Rosho's job. Especially wary due to Rei's tricks.

Rei makes no obvious note of Rosho's disapproval and instead shuts the door and leans against one of the student desks

"Sasara was wondering if you'd come for dinner tonight, he has a stand-up at a nice club-restaurant and is getting a free meal after his show. He invited us." Rei says, a weird smugness to his tone that doesn't have a reason for being there. Rosho was baffled, not by the proposal but by the fact Rei was here asking instead of Sasara just sending a text! Though technically the school was on Rei's route to wherever he was going how was he even allowed in!?