He tried to kill me. I saw my life flash before my eyes. Then, to my disbelief, I woke up to my life from a few years back. I had been given another chance. This time, I will not die. This time, he will pay.

Trust. It’s just a word, but it’s what got me into this mess. I told myself that I wouldn’t trust another human being and then I met him… Now look where it got me.

Areum is the younger sister of the doting Joonmyeon Kim. She lives as a normal high-schooler until a horrible incident throws her into the dark world of gangsters. She finds out that her loving brother is the leader of the gang Exo-K and even gets mixed up with its archrival, Exo-M. However, what the two gangs don't know that there is a bigger, more sinister gang who is their true nemesis.

Jiyeong is an orphan who is searching for her lost older brother. She decides to disguise herself as a boy and attend Taejong Boys High School in order to find him. When Jiyeong's best friend Jungkook persuades her to live at the House of Secrets, little does she know that her brother is closer than she would've thought. Also, she would've never expected to make such an impact on the lives of the boys there.