This drama is set in Sungkyunkwan University during the Joseon era, revolving around the exploits and love stories of four youths. When her younger brother falls ill, Kim Yoon Hee enters the school in his place disguised as a boy in her desperation to find a way to support him, and becomes friends with Lee Sun Joon - extremely rich and the brains of the gang, playboy Goo Yong Ha and the rebellious Moon Jae Shin.