Kanako's husband and his wife are busy, but her husband's younger brother comes to stay with them. Kanako is frustrated because they don't have sex at night, and although she is excited by men other than her husband, she hides it and fulfills her sexual desires by masturbating... When her husband returns from a business trip, he drinks some alcohol and goes to bed. Her brother-in-law, who knows the female heart inside and out, embraces her on the spot, and they have a forbidden cuckold encounter where she cannot resist. Her brother-in-law's hard cock relentlessly attacks her wet pussy, and Kanako climaxes, desperately trying to keep quiet so her sleeping husband doesn't find out.