Married for three years, Yuu is a wife who lives a happy married life, although she feels a little unsatisfied with her indifferent husband. One day, her brother-in-law Kensuke, who is an exercise trainer, comes to the house. Yuu has recently become concerned about her sagging body, and at her husband's recommendation, she decides to get some training... However, unlike her husband, Kensuke is a carnivorous man who was excited by Yuu's huge breasts from the moment he saw them, and under the pretext of training him, he plays with her voluptuous body. Before long, he can't resist the sensuality that oozes from Yuu's heated body and grabs her breasts...