Rei, a mother who lives happily with her daughter and her husband.However, her underwear was lost, and she witnessed her son-in-law Takeru masturbating it.It seems that the sexlessness between the couple is the cause.Rei, who sympathized with his decachi ○ port that is not used at all, seduced Takeshi while estrus saying, "I will help you instead of my daughter."Even though he knows she's the mother of her daughter-in-law, Takeshi, who can't control her excitement at her foolishness, exposes her erect decachi ○ port to her.