The first few episodes look really good. Stylized, atmospheric, poetic even ... packed with Wicked (pun intended) action scenes. Unfortunately, all that is gradually replaced by stale and pathetic melodrama and romance that redefines terms like corny and cheesy.
Basically, from Wow to yawn to wtf and finally to "Oh god, please, just don't" ...
There is also the completely unnecessary subplot of the rivalry between the main hero and the main heroine, extremely poorly presented, even worse maintained and resolved in a totally anti-cathartic manner.
On top of that, in typical Korean style, the dialogues are not realy dialogues, but extended spoken description of the scene. Do they really believe that the average viewer is a total idiot who needs everything drawn?
It's not all black, of course. Even in the later episodes there are flashes of inspiration here and there, especially the ninth episode and its atypical humor (the scene where the fat Japanese squeezes the wounded hand of the main villain out of gratitude is a real gem, I'm still laughing)
But all in all, lukewarm, bland and mostly boring. A missed opportunity.