...Okay I am super curious about the Otome AU you got going on
The moment Izuku got Isekai'd as the Demon Lord, he immediately sneaks into the Generic Fantasy Magic High School and seeks out Groundskeeper Sorahiko because he's curious to know which of the Sorahiko Routes from the Prequel Game is canon. He is delighted to learn that in this universe, the good ending of both routes are technically canon with Sorahiko marrying Nana after they seal Demon Lord Hisashi into a statue and convert his old castle into a school.
As soon as Ochaco got Isekai'd as the Villainess, she first seeks out each of the potential love interests for the Main Character and immediately tries to befriend all of them. She is unaware that the Demon Lord is actually her best friend from her previous life. She's more excited for when the Main Character finally arrives at the school, because that means she can hopefully befriend her.
Momo, who also got Isekai'd as the Main Character, instantly seeks out the Villainess because she will get her "Befriend the Villainess Route" no matter what! She doesn't want any of the romance routes because she finds all of the possible romance options uninteresting.
All for One is aware that his world initially existed as a Game Series/Light Novel Series. He is actually the cause of all of the bugs in the original game, and revels in the chaos that should eventually come with the people from this other world being brought into his domain.
Yoichi is also alive, working as a teacher at the Generic Fantasy Magic High School. He just doesn't tell his brother this and opts to let him continue to believe he is dead because this is hilarious to him. He is also aware that the world was originally a Game Series/Light Novel Series.