Mother Rei, who lives happily with her daughter and son-in-law, experiences a loss of underwear, and witnesses her son-in-law Takeshi using it as a masturbation aid. It seems to be due to the couple's sexless relationship... Feeling sorry for his unused large penis, Rei, in a state of arousal, tempts Takeshi with the words 'I'll help you in my daughter's place.' Despite knowing she is his mother-in-law, Takeshi cannot suppress his excitement at her lewd behavior, and reveals his rock-hard large penis to her...
