Chisato lives with her husband and stepson, but one day her younger sister Shinobu arrives with her own son. As they begin living together, each hiding their own family troubles, Shinobu accidentally witnesses her older sister committing adultery with her stepson. The shock creates a deep rift in her heart, sparking feelings of jealousy. From that day on, Shinobu becomes consumed by masturbation to satisfy her own desires. Meanwhile, the sexually frustrated mother begins a physical relationship with her son. Within this tangled web of sisterhood and parenthood, complex layers of jealousy and lust spiral out of control, intertwining hidden emotions and deepening into messy, intense sexual relationships. In the end, it's up to the viewer to determine who truly loves whom—and who hates whom.