During her husband's single assignment, Yoko, the mother, is staying at her daughter's house. She has been living a lonely life without her husband, but she was not the only one who was lonely. Her son-in-law, Tooru, was always masturbating alone at night, and when Yoko found out, she couldn't feel it was someone else's business... Knowing the pain of not being satisfied sexually, Yoko told herself that her daughter's responsibility was her own responsibility and began to invite him whenever she had the chance. But before long, in order to satisfy her own sexual desires, she continued to tempt him all day long, craving her son-in-law's big cock...