After her husband was transferred for work, leaving her alone, Hinami found herself overwhelmed by loneliness and began repeatedly cheating. One day, while engaged in a phone sex session with her lover, she was accidentally caught by her stepson, Yuuichi. From her voluptuous body dripped sweat, saliva spilled from her lips, and endless streams of arousal flowed from her crotch. Witnessing his stepmother in such a state, Yuuichi felt not anger, but an overwhelming desire, and suddenly made her an offer: "Let me take Father's place and be your man."