Sonoko Kiritani, a 46-year-old housewife from Kanagawa Prefecture, has been married to her office-worker husband for 22 years and is the mother of two children. Passionate about music since childhood, she graduated from music university dreaming of becoming a professional singer. However, during college, she became pregnant with her boyfriend—now her husband—and chose to give up her dream to focus on family life. As a hobby, she enjoys singing late into the night at karaoke with a group of friends. It was within this group that she made a mistake with one of the men, an affair that ultimately changed her relationship with her husband. "Until then, my husband and I had sex about twice a month, but after cheating for the first time, I realized just how loud my moans could be."