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.