First things first, it was a great choice making this a seven episode drama. In my opinion if this was 16 episodes, like some previous series like The guest and Save me, it would probably become a little boring halfway through and then it would be great again in the last few episodes.
Secondly, this was a series that I was (im)patiently waiting for every week. I loved the story from the beginning with that dark vibe that OCN knows how to handle. I liked all the twists that the show had to offer and the acting was good (in my opinion at least).
Finally, the whole psychopathy thing made me shiver as I though all of the characters previous scenes, including his intense feeling about sadness and sorrow and the will to avenge for everything that he lost. Even though this is not the first time that that kind of twist has appeared -and it will probably not be the last- the cruelty from the character and the understanding from the viewer that no matter what happened he didn't feel anything, was enough to make this show a great watch. I liked all the characters in this series and I would probably watch it again as it is, as I mentioned before, a seven episode drama.

The only complain that I have is the ending. I suppose that OCN is preparing for a new season, but I believe that if they had finished the series properly and without plans of making another season this would be even better.