Wife Miyu Kanade eagerly engages in creampie sex with her husband, hoping to deepen their marital bond and conceive a child. One day, her mother-in-law, Hitomi Enjo, comes to stay at their home. Overwhelmed by her husband's intense libido, Miyu suppresses her discomfort and pleases him discreetly—giving him a saliva hand job and swallowing his cum during 69 positions—all while trying to accommodate her mother-in-law. In truth, her husband and Hitomi have long shared a secret physical relationship, indulging in anal licking and vigorous cowgirl-position sex whenever alone. When Miyu accidentally witnesses their affair, she becomes entangled in a taboo incestuous threesome with the couple, gradually surrendering herself to the depraved pleasures of their carnal union.