Miho has been married since her youth and raised a son, but her relationship with her husband gradually cooled over time. Sexless days became routine, and by the time her son entered college, she discovered her husband's infidelity. Preparing for divorce, she began living separately—until her son returned home for summer break. Just as Miho planned to announce the divorce, her son confessed, "I'm in love with you, Mother." Drawn to her son's warmth in contrast to her cold, unfeeling husband, she's overwhelmed by forbidden maternal guilt and feminine pleasure. At a small mountain inn, mother and son lose themselves completely, forging a new, taboo relationship... A mother-son incest story.