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...

Young-mi is having a hard time because of her boyfriend Tae-sung who always tries to sleep with her when they meet. One day, Tae-sung suggests an interesting game and sleeps with a woman who approaches him and keeps it a secret from Young-mi. When they are together, Young-mi happens to see a text message from 'this woman' to Tae-sung. Then, she starts doing something unexpected...