Jong-hwan's friend's daughter Seong-hye moves into his house. She messes up the house and drinks with her friends and even has sex with men in the house. One day, Jong-hwan ends up comforting Seong-hye who broke up with her boyfriend. They spend more time together and become dependent on each other. Afterwards, they fall for each other more than they should...

Gyeong-soo and Jeong-min used to be the happiest couple in the world. However, Jeong-min is left home alone after her husband leaves to the regional area for a lengthy business trip. While she tries to deal with her lonely feelings, her son’s tutor Min-hyeok starts flirting with her hard. And although Jeong-min knows she shouldn’t, she starts being attracted to Min-hyeok more and more. Meanwhile, Gyeong-soo finds his place in a boarding house in the regional district and starts getting attracted to the owner of the board house, who is a single mother with a young daughter.

Are we dating? Even if I slept with her? Is it alright for friends to sleep with each other? Pretending not to know, pretending to know all the flirting going around. The flirting goes on any time and at any place! Today with this one, tomorrow with that one and who knows who the day after...

"Trust me tonight" Min-ho is preparing to get a job and is spending some time in his parents' house. However, his parents aren't home and only his young sister-in-law is there. His brother Hyeon-soo had left the house after fighting with his wife. Min-ho can't help but feel attracted towards his young and appealing sister-in-law.