This was 16 episodes of dribble. Too long.
No tension, bland, nothing really special to show off ghost Agent K. He is No James Bond - miscast I think. You even had Song Joong-ki as a bank teller, why? A waste of his talents.
Everyone seem just to read their lines and move on.
There was a lot good actors but none of them seem to gel together. It looked awkward at times, long pauses.