Kim Do Hyung, who works as a bank executive and comes from a well-to-do family, has been dating his girlfriend, Yoon Joo Young, for the past two years. He asks her to marry him, but Joo Young is tormented by his proposal and is terrified that Do Hyung will find out about her checkered past. After Joo Young makes up her mind to accept the marriage proposal, she suddenly disappears without a trace. When Do Hyung files a missing-person report with the police, officer Cha Yoon Mi is surprised to learn that Joo Young is someone she knows from her past but can’t offer much help to Do Hyung. When Do Hyung undertakes the search for Joo Young on his own, he is drawn into the shadowy underground world of gangsters and loan sharks. When Song Hak Soo, the leader of an underground crime syndicate who was recently released from prison, suddenly shows up dead, Do Hyung inexplicably becomes the prime suspect in the murders of Hak Soo and Joo Young, although she is still missing. With Yoon Mi and her partner, Park Hyung Shik, hot on his heels, can Do Hyung find Joo Young and clear his own name?
Kim Yun Hee is a smart, responsible young woman with an independent drive. Since her father passed away she has worked to support her family, but also managed to do well in her studies. When her younger brother's illness worsens and their family is in danger of being evicted from their house for lack of money. In her desperation to support him, Kim Yoon Hee decides to take the men's only national exam under her younger brother's name and disguises herself as a boy. On the day of the exam, Kim Yun Hee meets Lee Seon Joon and becomes friends. Lee Seon Joon comes from a privileged background and also possesses good looks. He is also arrogant. They both pass the national exam and she has to share a room together with him at Sungkyunkwan University, while hiding her true nature. There, she becomes friends with the playboy Goo Yong Ha and rebellious Moon Jae Shin.