Chisato lives with her husband and son-in-law. Her younger sister Shinobu brought her son to her house. One day, her younger sister Shinobu witnesses her older sister having a lewd relationship with her stepson. Her feelings welled up in her sister's heart... jealousy of her sister's sex-filled life. From that day, Shinobu's masturbation days begin. And her frustrated mother finally had an affair with her son. Jealousy swirls between her sisters and each parent and child. Sexual relations that are mixed in mush become intertwined intricately.
