After her sons leave the house, Michiru puts on black lingerie to tease her husband and focuses on satisfying herself. However, her actions are caught by her eldest son. Her masturbation in the bathroom is also seen by him, and she deliberately flaunts her erect cock. While doing laundry, she notices her son's underwear, and memories of the bathroom incident come rushing back, making her unable to resist pleasuring herself again. At that moment, the eldest son emerges from the bath and begins to tease her. When the sons return home, the eldest son joins Michiru alone, inspecting her body and touching her hard cock. The family's relationship begins to reshape into a new form.