After his wife points out that Atsushi hasn't been getting enough exercise, he ends up training with his neighbor Aki, a gym instructor. However, Aki, who knows that he is not having sex with her, is frustrated and starts playing with his lower body under the guise of training... Being a sadist by nature, she can't endure it after just one or two times, so she even puts a chastity belt on Atsushi's penis and continues to control his ejaculation. She watches him masturbate, sits on his face, uses a dildo on him, gives him a footjob, etc... After a week of teasing Atsushi in various ways...