Eight years into her marriage, Yuki Sakurai felt unsatisfied with her relationship with her husband. Longing to experience the passion and pleasure of their honeymoon days again, she struggled with her loyalty and social expectations, unable to bring herself to cheat. Meanwhile, Nachi, the daughter-in-law of the Kurosawa family, fulfilled her husband's cuckolding fantasy by sleeping with other men. By chance, the two women discovered they shared a similar situation, and began a secret affair while maintaining their marriages. Eventually, they realized another striking similarity between them—the extraordinary size of their breasts.