This game is peak harem gameplay. Once you have them all in love with you, wandering the school and having them all fawn over you, then pulling them into the showers and ordering them to eat your cum out of each other's assholes. God damn dude
I'm sure I'm in the minority, but I like a good HTML game.
Anything is fine, save for maybe Unity. It can be executed well, but most of the time it's mostly just someone's project to learn the engine and it struggles to efficiently do things that Ren'Py can do out of the box.