Michiharu lives with his mother-in-law Satsuki and spends every day secretly staring at her outrageously sexual breasts. When his father-in-law carelessly leaves a bruise on her chest, Michiharu anxiously offers treatment. Yet the moment her huge breasts are exposed before him, all reason collapses and he begins roughly playing with her mature, voluptuous body. Satsuki feels guilty toward her husband, but her son-in-law's intense desire still makes her body respond.