It was so good, the plot was had me on the edge of my seat. We follow Ok Chanmi as she tries to solve the mystery behind her twin brother's death. She transfers high schools from Busan to Seoul to investigate. On the other hand, you have a boy, having given up on his life due to unfortunate circumstances, who decide to help her while leading a secret double life at night as one who avenges those who are wronged by the powerful at their school. It was kind of violent at times, but super satisfying at the time. I really was loving this drama, but the ending really ruined it for me. I can't say too much without spoiling, but I didn't like how they chose to explain the motive behind the brother's death and how they managed to conceal everything for the duration of the show. Even tho I didn't like that, I still think its a good drama and one that I have re-watched bits of several times.