While her husband is away for work, Nami copes with pent-up desires by exercising. One day, while training with Kousuke, her son's athletic friend who shares her passion for fitness, she accidentally exposes herself, causing him to get an erection. Intrigued, Kousuke teasingly seduces her. What starts as a playful encounter quickly escalates—his unstoppable stamina remains undiminished despite repeated ejaculations, and Nami is forced to orgasm again and again. The pleasure intensifies uncontrollably, driving her to mind-blowing climaxes. Eventually, her overstimulated body can no longer endure the relentless assault, breaking down in overwhelming ecstasy.