With two months left before my wife gives birth, her mother Mayuka comes to Tokyo to help take care of us. Her presence eases the mood at home, but things remain tense between my wife and me because she caught me masturbating in secret and banned me from doing it again. Unable to resist the alluring Mayuka, I sniff her underwear while she is in the bath. I become so absorbed that I never realize she has caught me, setting off the repeated breeding sex that follows.