Momoko marries a man with an adult son. Her relationship with her husband is good, but she and her stepson Naoki never grow close and remain awkward around each other. Worried, her husband plans a family trip. Naoki, however, sees Momoko not as a mother but as a woman. Unable to suppress his desire at the sight of her unguarded body, he sneaks into her bed at night. His cock drives deep with piercing force and his powerful thrusts seem endless. Momoko's body discovers perfect sexual chemistry with Naoki unlike anything she has felt with her husband.