The ratings are so low I'm baffled. It's the similar situation like the drama Cheese in the Trap. People seek for a cliche romance or a thriller in this case, but when it's a bit unique, people immediately don't like it.
This series is a must watch. You cannot compare this to American crime shows because culturally it's very different. Korean standard wise, this series is outstanding. The bg score, the actors. Plot had a few problems but the way the actors carried it worked it out.
It may seem unrealistic at some instances, but then again it's a work of fiction so what are yall expecting??