Song Seunghoon is the head of one of the most famous gangs of the city, Blue Blood, he has over 700 people working for him in storing, smuggling, using drugs all over Korea and even in some other countries. His dominion makes everyone become wary and terrorstruck of him just by hearing the name.

However, his daughter is the purest and most innocent young girl in the world, Song Jieun. She is a university student, living a happy, carefree life thanks to not knowing what her father is doing. Unlike what he's famous for in his dark world, Song Seunghoon is a bright father who only teaches his daughter every beautiful thing with hoping her to grow up as a strong, independent, warm-hearted woman.

Jieun is a simple-minded girl, she tends to have good impressions on others and is easy to forgive. She believes her father is the most wonderful person in the world.

Bang Yongguk is a young police man, he's just graduated from school and got accepted to the biggest police foundation of the city headed by his father. He's an enthusiastic, active and optimistic young man, and always determined to be the best police man, just like his father.

Plot: They first met when he was doing his very first mission in his police career, capturing a breakout killer. He literally bumped into her upon chasing after his target..

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