Reiko deeply loves her son. Without realizing it, their relationship as mother and son has crossed boundaries, embracing each other and indulging in forbidden emotions. She planned a private getaway to a secluded hot spring inn with her son, wanting to spend time alone together. After check-in, her son immediately approached her, desiring intimacy, but Reiko, remembering her role as a mother, invited him to the private open-air bath instead. In the liberating atmosphere, when her son kissed her, the two could no longer restrain themselves and began passionately seeking pleasure from one another. A man quietly filming the scene was actually Reiko's former lover. Earlier, when the mother and son met at the entrance, he had passed by unnoticed. After their bath, as Reiko walked down the hallway, the man called out to her. Hearing her name, she grew suspicious, but soon realized it was her ex-lover. He showed her photos saved on his phone, exposing her relationship with her son. Seizing the shaken Reiko, he dragged her to an isolated place. Her sensitive body responded against her will, experiencing unwanted orgasms under his touch. She managed to make him cum with a blowjob, but he then took her to a room and raped her. After being repeatedly made to climax by the men, she staggered back to her room. Following dinner, she opened her body to her son's advances, yet found no satisfaction in their encounter. Late at night, she headed alone toward the men's room.