This is one of my absolute favorite K-action movies!
I've watched this movie the first time when it came out and rewatched it again now, even with all movies I've come across between and, in my opinion, it's the last decent K-action/thriller movie made so far.
First of all, the actors. Wow! Honestly, Siwan surprised me with how he absolutely nailed this role, Kyung gu is exactly how you'd want the actor for this role to be, and the chemistry between them is top notch.
The movie is not slow pased at all, it's more of a calculated, fermented thing, where every scene and every line has to have a perfect impact. Even better that is switches between past and present to give more depth to characters relationship. This movie is a masterpiece.