Monster Girl University

Turning 18 gets you out of your dead-end village and into Eldryck University's alchemy program, despite the fact that you know nothing about alchemy. That's the setup, and it's mostly an excuse to get you on campus.

Once there, the real work is settling in: pass yourself off as a student, navigate school life, and build relationships with the monster girls around you. Progress comes through the usual sandbox loop of managing your days, solving puzzles tied to your classes, and steering conversations toward romance rather than expulsion.

The endgame is the harem itself, assembled one relationship at a time rather than handed to you. Nobody said alchemy would be involved.