Momoko marries a man with an adult son, Yuta. She wants to grow closer to her stepson, but he continues keeping his distance. When she asks why his grades have recently fallen, Yuta admits that he cannot control his sex drive and has become obsessed with masturbating. Determined to guide him as his stepmother, Momoko uses her own body to give him sex education. Yuta repeatedly climaxes under her strict ejaculation control, and thanks to Momoko's efforts, the distance between them gradually disappears.