Semerare: Imouto de Kanjiru nante, Onii-chan wa Hentai Nanda ne

Ryou is a teacher with a secret he can't share with anyone: his younger sister Saori. To the outside world, Saori is a model student with perfect grades and a sweet demeanor. But in private, she is selfish and manipulative, using sexual games as a way to relieve her stress and tormenting Ryou.

Ryou longs to escape this dangerous relationship. When a female colleague confesses her feelings for him, he sees a chance at a normal life. However, Saori discovers their encounter and threatens to expose him, trapping him further in her web of control.