After losing her husband, a successful spa business owner named Mika is forced to live with her son Shunsuke and her late husband's younger brother and his wife. Shunsuke harbors secret desires for Mika and spends his days indulging in masturbation, while the younger brother and his wife grow increasingly frustrated, deprived of physical intimacy. Exploiting Mika's loneliness, they coerce her into sex. Witnessing the act awakens uncontrollable lust within Mika, driving her to seek pleasure through self-pleasure. Soon, her brother-in-law begins touching her, while she herself starts orally pleasuring Shunsuke's erect penis. This depraved family dynamic reaches a turning point on the first anniversary of her husband's death, when a shocking will is revealed—one that will drastically alter Mika's future.