My standards were pretty high with this one and it didn't disappoint me at all.
-First of all, the cast: I already heard about Park Jihoon's talent but I had never seen any of his works and all I have to say is that I am AMAZED. His character is portrayed flawlessly and his eyes had me amazed the whole time. Likewise, want to mention Hong Kyung's acting (Oh Beomseok), which also mesmerized me. All the casting was done perfectly.
-The story might seem like one of these typical bullying stories at some schools but I think it goes way deeper than that and that's what fascinated me.
You get to be on the skin of the characters and you can feel them and understand them, even when they do morally incorrect things.
-It has many fighting scenes, which some people might dislike but I honestly liked it because it showed the depths of the characters and how far they could go when they lost control.

As I said before. If you have the time and the opportunity to watch it, go and watch it ASAP. It is truly a gem.