I saw @frant1cfawn say there needs to be more Bet Au’s and I couldn’t agree more so walk with me (most of these ideas aren’t in-depth or well thought out I’m just throwing spaghetti at the wall):
-Dnd au: Scrap betting the school is actually a DnD school a place where you start with a character and level them up through a multitude of challenges tasks and tribulations throughout your time at the school.
-Lab au: where all the parents fund a lab to create superhuman soldiers or something and use their kids for it plus or minus some random kids they kidnapped for more numbers. The kids get extra abilities and stuff but with a ton of downsides to each one. (I imagine Yumekos parents tried to get her out and succeeded for a few years and when she gets found out and taken back that’s where the reintroductions start).
-Camp counsellors au: each student council member gets a cabin (this includes Yumeko) and a bunch of summer hijinks ensue. (Very competitive)
-classic soulmate au always hits
-I think I’ve seen this before but Band au with the student council members
-Hunger Games Au with Arkadi and the board members being kinda snow like characters and sending their kids into the games to toughen them up
-Percy Jackson Au Parents and Gods suck here
-Time Travel au: Yumeko, Ryan and Mary (or some group variation) accidentally travel back in Time while exploring the old abandoned school building that has horror stories written from its opening till its eventual closure for unknown reasons 30 years before the group steps foot on the property. It follows as they are transported to just before its closure and maybe they’ll find the reason for the shutdown along with some people they meet at the time.
-Avian Au: everyone has wings, some better cared for, some not, some big, some small, most fly, few don’t.
Some more specific Riri x Mary Au’s
-Soulmate Au: the first place your soulmate touches you is marked and Riri has a hand mark on her face so she hides it with a mask not knowing that it’s Mary gently cupping her face before she kisses her.
-Reverse Au where Riri falls out of favour with Kira and drops from council leading to Mary being the right hand and Riri temporarily being a house pet.
-Cat share au: they both think they’ve been keeping a cat as their pet on school grounds but the cats been moving between their room without them noticing until they do.
-Fake dating au: Riri finds out Arkadi is going to put a hit on Mary cause he doesn’t want a non legacy that high on the leaderboard. Now the only way to protect Mary is to pretend to everyone they’re together. It’s probably doesn’t help that Riri has had a secret Crush on Mary for a while.
-Met as children on holiday and never forgot it only to meet again at st Dominic’s
This is some ideas I came up with and please if you use them tag me cause I’m losing it waiting for season 2.