The acting, the scenes, the OSTs are literally perfect. Only negative thing, I guessed the entire plot in the first/first and a half episode. That was a little disappointing, but I guess it is possible when you consume a lot of crime dramas. Apart from that, it is really wonderfully secured, and MUST be watched entirely, because (and I cannot stress it enough) the ACTING is superior.
Also really liked the cinematography, the action scenes were beautifully executed and coreographed.