After three peaceful years of marriage to a kind husband, Riho Fujimori unexpectedly reunites with Oshima, the coach she admired during her adult school-club days. Perhaps pity for his lonely appearance makes her cross a line she knows she should not. He repeatedly makes her cum with his fingers and tongue, and before long obeying his commands feels natural. Through relentless pleasure training, she becomes both submissive and sexually aggressive, hopelessly addicted to sex with him despite the shame and humiliation.