In an ordinary-looking house, live the owner couple, Se-kyung and Jung-sik, their daughter,Ma-ri, and Jin-seong who's new to society. The couple is on vacation, and Ma-ri and Jin-seong are alone in the house. One ordinary day, An Uninvited Guest called Soo-jeong comes along. She had a fight with her husband and had come to stay in her brother's house for a few days. However, one night Soo-jeong gets drunk and mistakes Jin-seong's room for hers. As a result, they end up sleeping together. Ma-ri sees Soo-jeong come out of Jin-seong's room, but suspects nothing else. Vegetarian Jin-seong craves sex and sleeps with Soo-jeong once again. However, Soo-jeong goes back to her husband, and Jin-seong can't help but feel lonely. Meanwhile, Ma-ri likes Jin-seong and seduces him to have sex with her, but she's outraged when he tells her he had sex with her aunt. This is the story of the ordinary but not so ordinary, secretive house.

Sun-gyu was looking for a house when ends up living in Ji-won's house. One day, Ji-won is having phone sex with her boyfriend in the living room and Sun-gyu dreams of having sex with her. In the end, he gets a call girl to fullfill his needs but it's not enough. Meanwhile, Ji-won is looking for her missing underwear when Sun-gyu comes home and she approaches him...

Sung-chan and Soo-jin used to date. Soo-jin was expecting quality time together until he comes home drunk. A few years later, they break up and Soo-jin appears in front of Sung-chan who is about to marry Yoo-ri. Sung-chan and Soo-jin still like each other and they both desire each other. Will Sung-chan be happily married?

Hyeri and Ji-yeon are friends in the same neighborhood. They have a son to go to the army after some time. One day, Min-gu, who was playing at Jun-suk's house, sees Jun-suk's mother Hyeri in the shower and gets excited and hits her. Hyeri, who initially resisted, gave up resistance to Mingu's power, and after that day, the two develop into sex every time they have time. After a few days, Ji-yeon, who accidentally witnessed her son Min-gu and Hye-ri having sex, begins to seduce Hye-ri's son Jun-seok.