Chisato has remarried and married into a new clan. In her new home, she has a stepson, but because she remarried an older man, her husband is more reserved at night. On the contrary, she and her stepson are quite close in age, and they tend to be nervous and nervous of each other. One day, when her husband was away on a long business trip and she had too much free time on her hands, her stepson happened to come back early and saw the whole embarrassing act. He takes advantage of her weakness by saying, "Instead of keeping quiet," and gives in to her stepson's lewd desires. From that time, the secret thing with the stepson continues by the thing which allowed the body....