I adore this show, so so much. I truly enjoyed it so much and had practically no grievances with it. The one or two I have are truly opinion-based and I don't truly consider them as flaws. Shall I begin?
Story, 10/10:
Where to begin? I think the supernatural element of this show is really interesting and I enjoy true crime so I liked that aspect as well. The group of ghost hunters isn't a new concept but I think the way it's done in this show is really fun. My two grievances fall into this category so I'll say it now. 1. I wish they'd kept So Hun disabled and he had learned to fight well despite it. I am most definitely biased since I myself am disabled and walk with a limp. Mine isn't injury based so it's a little different but still. My second and last grievance is that I wish they'd focused a tad bit more on the supernatural parts. They did in the beginning and don't get me wrong, I enjoy the true crime element quite a lot but I would've enjoyed a bit more evil spirit hunting. Also, the evil spirit villain in this show is scary as hell and I hate that high-pitched giggle he does.

Acting, 10/10:
I found absolutely no issues with the acting. I thought everyone was superb and I can't think of anyone whose acting I disliked. My favorite acting probably would come from the guy who plays the evil spirit villain. He is so scary and I get anxious every time I see him on the screen.

Music, 8.5/10:
The soundtrack was good but I wasn't blown away. I've heard better but I've also heard worse. This is on the higher end of the averageness scale. If you want to hear some good drama music, try watching Doom at your service or Hotel Del Luna. Both are killer though I prefer DAYS over HDL.

Characters(I know it's not a category but I'm including it anyway):
My favorite character is So Hun, no competition. He has such a sweet personality and I truly relate to him. I am really emotional and I am disabled so I clicked with him instantly. My second favorite character is Ha-Na, she is so badass. She is also really pretty. My third favorite is a tie between the former policeman and the healer lady. I hate that I forgot their names but that doesn't mean I don't care for them. I hate the villains so much, I can't pick who is more loathable. Also, So Hun's friends are great and I like them a lot.

Rewatchability, 9/10:
I don't tend to rewatch things and I doubt I will rewatch this but that is just me. For anyone else, I think watching a second time would be pretty fun. Not as fun since the suspense would be gone but it would still be fun.

Overall, 10/10:
Please, please, please watch this show. It is really good and I wish more people were talking about it. It is one of the best drama's I've watched and I hope you'll like it as well. But a bit of a warning, it can be a bit gruesome and bloody but nothing too gratuitous.