Rin visits her in-laws' home with her husband to check on her ailing father-in-law, Eikichi. That night, Rin is caught by Eikichi while she is masturbating, leading to an unexpected turn of events. To her surprise, Eikichi, concerned about the couple's sex life, says, "If you take care of me, I'll teach you what sex is all about!" and proceeds to fondle his daughter-in-law in front of his son. Then, the father-in-law's "SEX lessons" escalate further...
