Yeong-jae (Sin Joo-ah), Ha-eun (Koo Ji-sung) and Chun-hee (Yoon Chae-i) have been friends for 15 years since high school.Yeon-jae is the youngest of a fine hotel owner and she aims to sleep with 1203 men throughout her life. On the other hand, Chun-hee is an old-school minded high school teacher who has never had sex before in her thirty-something life.Wedding planner Ha-eun was in love with one man for 10 years but recently experienced the pain of losing both her man and work.Then one day, to celebrate their 10th year majority, they have a party of their own in room 1203 of Yeon-jae's hotel.They say the house breaks down if three girls get together.Just turning thirty, the 3 girls' talk goes overboard, going further than adult rated. Soon, they start poking at each other's nerves and end up making a bet; they have to meet a man and spend a hot night with him.They target the hotel bellboy Hyeon-soo (Lee Yeong-hoon) who looks just like the guy at school all three of them used to like.To prove their night with him, they must collect a sample of their semen. Who is going to spend the hot night with him? Who slept with the hotel bellboy?