WHAT I LIKED:
- The many characters with different personalities and tempers. They are able to form a good team supporting each other. The relationship between them is well told.
- The background story of the counters. Each of them has a well made backstory which give them depth and makes them endearing.
- The pace: the drama is fast paced with a lot of good action. I enjoyed the fights.
- The mix between thriller and supernatural is pretty well made even if I wished the realtionship between the bad humans and the evil spirits was stronger and lasted longer
- The supporting characters are interesting: the sponsor, the female cop and her trainee, the two friends of Mun...
- Most of the actors are very good.

WHAT I DID NOT LIKE:
- Too much unnecessary violence
- Sometimes repetitive: Abducting someone and making a call to threaten to kill him. This is done several times
- Some flaws in the story: How come visiting your own memories can lead you to enter the memories of another person and fight in his memories and so find where he is hidden. It is a stretch.
- Some events and elements do not serve the story and are just here to create emotions: the ankle broken and repaired several times, the bullying and beating by the schoolboys thugs, the kid with disease, the orphans, the old folks... plenty of usual tropes.
- The main lead allways accuses himself of being responsible for everything bad happening and cries too much. It became annoying in the end.
- The story is thin: they catch bad persons and evil spirits. It was so thin, from the middle of the drama, it started to be draggy like they don't have a good story to tell and they focus on creating repetitive and useless scenes focusing on the characters' emotions. The bad guys are catched way too easily between two emotional scenes. The final fight was also disappointing.

OST: It was ok for the genre.

REWATCH VALUE: I won't rewatch it.

OVERALL: This drama is a huge success. Personally I found it was emotionally a roller coaster ( a bit too much sometimes) but storywise it was not so interesting. It is entertaining mostly because of the sympathy you have for the main characters, their story and their suffering and their success but I was clearly not amazed by the complexity of story. I still recommend it as a good and easy watch.