After Seo Haneul (Sung Yu Ri) lost her mother in a fire, she was later adopted by a wealthy family and experienced a life of many twists and turns. Seo Gun's (Gong Yoo) father had married an unwed mother, thus making Seo Haneul his sister in the eyes of the law. After their parents passed away, Seo Haneul was adopted by a wealthy chairman of a large organization who has also became a gangster. Upon using Haneul to extort money, Seo Gun and Haneul slowly fall in love with each other.


Cast
* Gong Yoo as Seo Gun
* Sung Yu Ri as Seo Ha Neul / Park Hae Won
* Lee Yeon Hee as Goo Hyo Ju
* Nam Goong Min as Kim Dong Ho

Extended Cast
* Lee Eon Jeong as Choi Seong Kyung (Gun's friend)
* Ahn Yeon Hong as Kim Mal Ja (Ha Neul's friend)
* Woo Hee Jin
* Jung Dong Hwan as Park Jin Kwon (Ha Neul's adoptive father)
* Sun Woo Eun Sook as Ji Soo Hyun
* Yoo Ha Joon as Park Tae Won
* Kang Sung Jin as Goo Seong Chan / James
* Lee Ki Yul as Goo Kyung Taek (Gun's adoptive father)
* Suh Ji Hee as young Ha Neul