Chisato Shoda, who remarried and joined a new family, was trying her best to adapt, but her relationship with her stepson was somewhat complicated. Her husband, due to their age difference, wasn't very active in bed and lacked enthusiasm. On the other hand, her stepson was closer to her in age, and though both felt tension, they were increasingly drawn to each other. One afternoon, while her husband was away on a long business trip, Chisato found herself with nothing to do and began masturbating for the first time in a while. Suddenly, her stepson returned home early and accidentally caught her in the act. Seizing the moment and using her secret against her, he demanded she satisfy his desires in exchange for his silence. From that moment on, Chisato's relationship with her stepson changed drastically, and their forbidden affair deepened gradually. Entangled emotions sparked a new, illicit romance filled with intense desire.