Gangseo, while having sex with his girlfriend these days, often thinks about her older sister. He always blames himself for being a pervert, but he just can't help it. One day he saw a sexy performance, and his body reacted instinctively. One day, Kang-seo listened to the sound of his older brother, Chan-jun, and his quarrel after sex. From Chan-jun's own words, he finds out that the performer is a room salon waitress...