49-year-old mother Iori Ryouko raised her son alone after losing her husband. To ease her loneliness, she secretly pleasured herself every night. One day, her son's friend, who was staying over, discovered her masturbating and immediately raped her with his young body. Witnessing the scene, her son—driven by twisted affection—bound her tightly and began training her as his sex slave. As both the son and his friend repeatedly take her, Ryouko's body endures an unending cycle of infinite pleasure and suffering.