Na-Nan has known best pals Dong-Mi and Jung-Joon since childhood, and now the trio shares the ups and downs of their turbulent single lives together. But everything gets turned on end when Dong-Mi and Jung-Joon end up in bed. Should the longtime friends make it official or call it a mistake? Na Nan has a job offer and a marriage proposal from the charming Soo-Heon to consider, and her twenties are fast coming to end. What's a generation of soon-to-getting-older youth to do?