Gong Yoo [Seo Gun], Lee Yeon Hee [Goo Hyo Ju], Sung Yu Ri [Seo Haneul/ Park HaeWon], Nam Gong Min [Kim Dong Ho]
Seo Haneul (Sung yuri) loses her mother in a fire accident and was later adopted by a rich family. She is a person who went through a life of many twisted fate. After Seo Gun's father married an unwed mother, since then Seo Gun has a sister in the eyes of the law. After their parents died, his sister was adopted by a rich Chairman of a large organization while he became a gangster. Upon using Haneul to extort money, Seo Gun and Haneul falls slowly in love with each other during this period of time.
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I have watch up until 12 episodes and I find it a great drama. It might drag here and than but it wants you to watch more . I heard it's currently the most fav. show in korean right now [as in korean drama].