Asahi, whose hobby is weight training, finds out that her son's friend Kentaro is not getting enough exercise, so she starts teaching him... When she accidentally touches the size of his crotch, she remembers the sexual desire that cannot be released through training alone. And Asahi, who has no choice but to give in to her desire, plays with his cock and seduces him... However, his virility doesn't end after just one or two times, and her body climaxes again and again, and she continues to cry out in agony. Asahi finally gives up on the seemingly eternal sex with him...