Magical Girl Miyu

A volleyball club girl gets handed a magical-girl transformation just in time to fight off three succubus sisters, only to find out she's less "chosen hero" and more "ideal specimen" in their eyes. Each sister has her own curriculum, some of it pleasure, some of it BDSM, all of it aimed at breaking down whatever power she just gained.

Miyu doesn't lose because you fail her. She loses because that's the point. The battles run on an auto system where she picks her own "best" move and gets overwhelmed anyway, so you're not steering her toward victory, you're watching her earnest, doomed effort play out. Combat is the setup, not the goal; what follows the loss is where the game actually lives, and it keeps going well past the point a normal fight would end.