Reiko married a divorced man and started living with his stepson, Atsushi. Reiko devotedly did her best to build a happy family by doing the housework. One day, she witnessed something so shocking that she thought she must be mistaken. While relaxing in the living room, Atsushi noticed a surprising swelling in his crotch, which he was casually touching and smoothing out. Reiko lost her mind at the swelling, which was incomparable to her husband's.