42-year-old Mio attends her high school reunion for a brief escape, where she falls into an affair with Ichijo. She becomes captivated by the pleasure of being held by a man other than her husband, indulging in the thrill of forbidden desire. With each encounter, her rationality fades further, until she surrenders her previously untouched anal virginity—unknown even to her husband—to Ichijo. The film portrays Mio's descent into an obsessive affair, consumed by desire. At the climax of her infidelity, she cries out, "Please forgive me... I can't go back anymore..." A gripping tale of a married woman torn between lust and guilt unfolds.