Stepmother Sayuri, feeling emotionally unfulfilled due to growing estrangement with her remarried husband and deteriorating relationship with her stepson, finds her life taking a dark turn when her affair with a lover is secretly recorded by her stepson. Exposed and humiliated, she gradually becomes his sexual plaything. Subjected to degrading treatment, she nonetheless craves his demands, her body responding with wet arousal as she is trained into becoming a flesh slave. The story unfolds her psychological transformation and physical submission as she descends deeper into a life of sexual servitude.