Sumire lives with her husband and son Koichi. Her son steals Sumire's underwear and masturbates while looking at the pictures, making it a daily routine. One day, Sumire accidentally witnesses this scene. "Why are you doing that while looking at my photos?" she confronts him, but he confesses, "I want to do it with Mom, I've always liked you." For a month, the mother continues to receive advances from her son and eventually gives in, crossing the line.
