A woman named Ayumi, married to a workaholic man and living with her step-son Kazuma, finds herself feeling lonely despite being happy with her husband. One day, she catches Kazuma masturbating and becomes aroused by his erect penis. As she watches him use a vibrator on himself, she can't resist joining in. Later that night, when Ayumi cannot satisfy her desires with her husband, she sneaks into Kazuma's room while he's sleeping and begins touching herself again. After hearing about Kazuma's struggles with girls, Ayumi promises to help him however she can - even if it means having hardcore sex together. As their relationship evolves, they become increasingly intimate, engaging in passionate intercourse filled with orgasms and multiple ejaculations. Despite knowing it's wrong, they continue to find solace in each other's bodies, creating an unbreakable bond through taboo incestuous acts...