Everybody really nailed their roles here. Especially Kim Seulgi, and Key, its my first time seeing them in an action drama. Though i think Solomon (Shi-wan) doesn't suit his character here that much. Every time he will try to look like a psycho something like he will smile and laugh low-key it doesn't look natural(?) like it's a force smile/laugh and it looks a little bit awkward for me.

Overall I'll give this drama a 7/10. I watched a lot of action drama (mostly on OCN) and in my opinion there's nothing really extraordinary in this drama but it's still great and the plot of the story is nice.