A 22-year-old ronin student confesses to an ongoing forbidden incestuous relationship with his female college student sister. Having played by showing each other their genitals since childhood, their bond deepened over time. Eventually, the sister completely dominates her younger brother, tormenting his anus with thick vibrators. Intoxicated by the pleasure, she increasingly uses him as her personal sex toy, making him serve her with vibrators and even her own flesh dildo. The impulses born from their taboo love drag them both into ever deeper depravity.