After losing her husband in an accident, Ayano raises her daughter alone until she marries. When the newlyweds move in next door so Ayano will not be lonely, she learns that her son-in-law Takuto is trapped in a sexless marriage and masturbates every night. Ayano has remained faithful to her late husband, but the sight of Takuto's huge cock destroys her restraint. She begins devouring it and helping him cum whenever she gets the chance, sinking into days of obsessive sexual service, while her relentless caresses gradually overwhelm Takuto in body and mind.