Tatsuo Wada, a university student living in Tokyo, stays with his mother Yukika Wada while renovating the family home. Living together are his aunt Hitomi Okumura, her son Yohei Okumura, and her younger son Yasuhiro Okumura. As the family adjusts to this new arrangement, Tatsuo, who had previously lived alone, continues residing under his mother's roof. One day, while planning a trip home with his mother, Tatsuo unexpectedly feels intense sexual arousal toward her. Ignoring boundaries, he indulges in repeated fantasies and eventually engages in an incestuous relationship with her. Meanwhile, Yasuhiro discovers that his mother Hitomi and older brother Yohei are involved in a secret intimate relationship, triggering feelings of jealousy and emotional turmoil. Witnessing Tatsuo's taboo affair with his own mother further destabilizes the household, throwing the family into chaos. Driven by resentment and desire, Yasuhiro devises a perverse scheme targeting Tatsuo. As familial bonds and hidden lusts collide, the situation spirals into irreversible consequences.