Simple premise: Yuichi is enrolled to the Advanced Nurturing Highschool from Classroom of the elite or Kiyotaka Ayanakoji is Forced to play the Tomodachi Game.
So whichever you write will be your MC, for example if you choose Yuichi enrolling then Yuichi/MC will battle Ayanakoji for Supremacy in either reaching The class A or battling For staying at the top. They both can't be at the same Class, so Yuichi is needed to be in the class of A,B, or C.
Make it an Self insert as It'll be ruined if it's a reincarnated person with meta playing as either one and Them being Transmigrated will be boring too.