Mr. Hwang is a known assasin, who keeps his identity hidden. He has a son named Hyunjin (almost 19), who is a rich spoiled student. So, to occupy his son from his dirty things, he wanted to hire a bodyguard. You were a 22 year old detective woman who've been in taekwondo for 18 years. One day, at your company, you get told that Mr. Hwang might be the criminal bc of his personality so the manager, (you were the youngest there), tried to convince you to be Hyunjin's fake bodyguard to spy on him