Ririko's husband had to go on a business trip alone, so she moved in with her daughter and her husband. Although it's better than having to live alone, Ririko still feels lonely and lacks sex. Every night she has to masturbate to comfort her body. She also discovered the shadow of a giant cock looming outside the door, it seemed like that person was also masturbating with her. She also guessed that person was probably her son-in-law. Discovering that her daughter doesn't like having sex with her husband because his cock is too big, causing her son-in-law to always have to handle it alone. Ririko immediately came up with a daring thought, which was to sneak into the couple's bedroom and soothe her son-in-law's giant cock! “It's all because of Keiko and Kunio-san”, “Blowjob doesn't count as adultery, right?”. Awakened, Kunio could not control Ririko's seductive body. The two continued to make love even though Keiko was sleeping next to him. Their bodies seemed made for each other, they continuously made love and climaxed over and over again whenever Keiko was absent. Both seem to be unable to live without having sex with the other...