Horie from the Takeuchi family runs a massage parlor with her husband. Dissatisfied with their sex life due to his poor erection, premature ejaculation, and indifferent attitude, she feels increasingly unfulfilled. One day, her daughter and son-in-law visit for a family reunion. Determined to relieve her son-in-law's fatigue, Horie gives him a massage while chatting with the family. During the session, she notices something strange about his crotch—it's unusually swollen, making her heart race. That night, waking up, Horie heads toward the living room and catches her son-in-law masturbating in the changing room. Telling herself it's just natural male physiology, she can't look away from his powerfully erect cock, swallowing hard as she watches the thick white fluid ooze from his tip. Before she realizes it, her own hand has slipped between her legs—panicking, she quickly flees the scene. The next day, her husband and daughter's couple go out. Horie invites her son-in-law for tea, but finds him napping. As she approaches to cover him with a futon, she can't stop thinking about his crotch from the previous night. Giving in to a mischievous impulse, she pokes it gently—watching it grow larger, she can't resist pulling down his pants. Drawn like a magnet, she presses her tongue against his crotch, licking him wildly and obsessively. That evening, her husband and the couple go drinking. Alone in the quiet bedroom, Horie recalls her son-in-law's powerful manhood, excitement building to its peak. Suddenly, she hears noisy footsteps as they return home. Her drunken husband is carried in by her son-in-law and laid on the bed. As Horie mutters to her sleeping husband, "You're really impossible," her son-in-law suddenly whispers, "You're no better, Mom," pulling her into a tight embrace. Though she pretends to resist for appearances' sake with her husband right there, Horie's heart pounds uncontrollably, completely captivated by her son-in-law.