Momoko is a married woman who married her husband in her later years. He has a son, Takashi, who is a university student. Even after three years, Momoko and Takashi still use polite language and have not been able to close the distance between them, but one day, she receives a package addressed to her. Recently, she has been receiving packages from the same company frequently, and Momoko becomes suspicious and decides to take a peek at the package when Takashi is out. When she looks inside, she finds a sexy swimsuit inside. She picks it up, and although she thinks how shameless it is, Momoko is tempted and puts on the swimsuit herself...