Let's Go To Rose Motel.

Seong-soo hasn't had any physical contact with his girlfriend yet after 6 months of being together so he's always excited to see her. One day, Seong-soo succeeds in getting Min-ae into Rose Motel. When he is about to shower, Seong-soo discovers a small hole in the wall leading to the next room and watches the couple next door having intercourse. Seong-soo continues to watch out of curiosity but realizes he just watched celebrity Sara giving sexual favors to a big shot politician...