RPGM Futa Prision

Futa Prison follows Sato, an ordinary university student who notices a magical portal in his room while about to play video games. Curiosity gets the better of him, and he steps through into a world ruled by futanaris, just as a fleeing thief uses the same portal to escape her crime.

The theft is pinned on Sato, and he is sentenced to a prison where the guards are 2.5-meter-tall women armed with massive red sticks between their legs. Now he has to escape a prison built to use men as sex toys. The 3DCG renders, animated scenes, 2D-game mechanics, big-ass and big-tits character design carry the look.

Female domination, futa/trans, harem, humiliation, internal-view scenes, and corruption arcs all factor into the escape attempt. If you want a futa-prison adventure visual novel with a clear setup, real worldbuilding, and a male protagonist pushed to his limit, Futa Prison commits to that scope.