Ririko's husband had to go on a business trip alone, so she moved in to live with the husband, wife, and daughter. Although it was better than living alone, Ririko still felt lonely and lacking in sexual activity. Every night, she had to masturbate to comfort her body. She also noticed the shadow of a giant penis peeking out of the door, as if that person was also masturbating with her. She guessed that person was probably her son-in-law. Discovering that her daughter didn't like having sex with her husband because his penis was too big, causing her son-in-law to always have to handle it on his own. Ririko had a bold idea, which was to sneak into the bedroom of the couple and soothe her son-in-law's giant penis! "All for Keiko and Kunio-san," "Is giving a blowjob considered cheating, isn't it?" Awakened, Kunio could not resist the seductive body of Ririko, and they continued to have sex continuously even though Keiko was sleeping next to them. Their bodies seemed to be made for each other, they constantly had sex and reached climax time after time whenever Keiko was absent. It seemed like they couldn't live without having sex with each other...