Bishoujo Mangekyou -Tsumi to Batsu no Shoujo-

A year in the hospital keeps Yuuma away from home, and when he finally comes back it's his twin sister Yuuri he moves in with, not a stranger. He's kept quiet about one thing this whole time: he's in love with her.

Living under one roof doesn't help him bury it. The story follows what happens once that secret starts leaking out, and how a feeling he can't admit to turns into something closer to fixation than affection.

You read through Yuuma's side of things, make choices that steer how far the obsession goes, and end up at one of several possible endings depending on how much restraint he shows, or doesn't. Voice work backs the scenes, and the art stays in the usual 2D visual novel frame throughout, no animation beyond stills.