Motto! Haramase! Honoo no Oppai Isekai Oppai Bunny Gakuen!

The head of the App Development Club has a cover story about wholesome extracurricular activities. What the club actually does is quietly build a bishoujo game called "Welcome to Impregnation Isekai Oppai Bunny Academy!" On parents' day, mid-debug, he gets pulled straight into the world of the game he was making.

That setup is the whole plot: a guy who loves boobs and bunny girls wakes up inside his own erotic game, at Usaki Academy, surrounded by exactly the kind of cast he designed on purpose. Isekai logic applies, so the rules of his old life stop mattering the moment he lands.

Play follows visual novel conventions, reading through voiced scenes and dialogue as the protagonist works out how his creation actually functions from the inside, with the academy setting, harem cast, and monster girls all doing what he built them to do.