Airi, a super busty young wife, is 26 years old. She started her married life with her husband, who is much older than her, Airi with her stepson, who is closer in age to her husband. One day, Airi, who was worried about the excess fat she had around her stomach, was given a leotard as a gift by her husband. The stepson, who had been troubled by the sexual life between his stepmother and his father, fantasizes about his stepmother in a leotard every day... And, unable to distinguish between reality and fantasy, he finally gets his stepmother...!