Couple Hee-joo and Woo-seok, who are in good harmony with each other, become increasingly provocative sex addicts. Unknown to Hee-joo, Woo-seok offers watching sex to his senior Jong-gyu, and Jong-gyu gets a thrilling experience. After having a taste of "spectator sex" Jong-gyu secretly meets Hee-joo and his girlfriend Mi-seon and the three of them have sex.