Mother, Seiko, and son Takeshi are very close as parent and child, and even confirm their love for each other through words. One day, Takeshi witnesses the mother handing money to a gigolo. The three of them discuss the situation, but in his rage, Takeshi ties up his son and begins to rape his mother in front of him. At first, the mother hesitates, but she begins to let out sighs, stops resisting, and lets him do as he pleases. The feeling of being raped in front of her beloved son stimulates her sexual desire, bringing her to orgasmic pleasure...