After a year of dating, Rumiko finally marries Kentaro and begins a new life with him and his son, Mansaku. Mansaku, who is slightly mother-dependent, is overjoyed to have Rumiko as his new mother. One night, he accidentally witnesses his father and Rumiko engaging in passionate, intense sex. Deeply aroused by the sight, he begins masturbating while fantasizing about his beloved stepmother. Rumiko discovers his actions but, rather than confronting him, quietly acknowledges his feelings as she contemplates the complex dynamics of their new family. A touching and bittersweet story exploring the bonds of family and the depths of forbidden desire.