I liked most of this drama, but had some issues with the overall story. This definitely could've benefited from a few more episodes to flesh out Jiyong and his backstory. The audience does understand why he's doing what he's doing, but I think it was an abrupt escalation from assaulting bad guys to killing them. And maybe I'm just dumb, but it took me a little bit to realize that he was actually killing the bad guys. In my defense, it never actually showed him finishing them off, and it seemed like he gave some of them an option to repent (ex: the rich guy who hit the old lady with the cardboard).
Beyond giving Jiyong more of a full character, a few more episodes could've given us more depth into relationships between the characters and made us feel more for them other than a passing interest (maybe it's just me, but I wasn't too invested in any of the characters and most of them seemed a little one dimensional. Other than Jiyong's Number One Fanboy. He was great.). I think the bad guys and their evil plan could've used more depth as well, but given that it was only 8 episodes, they crammed a lot into them and it was a complete story.
Overall, a decent and well-made drama, but needed a little bit more to really flesh it out.