I thought this started off well, though I’m going to say I found PHS miscast. I never fully bought him as a detective, especially a “bad cop” type.
That is not to say his acting was bad. I just didn’t think he was right for the role.
This may also have to do with not being a PHS obsessive as a lot of fans of this drama seem to be. Actually I didn’t recognize him at first because he put on a fair amount of weight and his face looks very different.

I initially fell in love with Sae Bom’s character, then got kind of annoyed when she made rather silly decisions early on and the show did that typical thing that kdramas and to a certain extent most tv shows do now where female characters are never taken to task for their poor decision-making. She got back on track as the show went on, though.

I took issue with the general attitude both protagonists had with the infected. They were cops, not doctors, so it seemed weird to me how self-righteous and ready to protect the zompires they were from the get-go. I could have understood it after more exposure to them, but from the start it didn’t make sense that they were so ready to protect them at all costs.

The illness makes no sense whatsoever. A drug can give it to you? And then you can spread it to someone else? Really? At certain points you have characters plotting to use the situation as an excuse to get rid of other characters. But when does anybody actually die from this thing? People get bitten and everyone just becomes a zompire. Except when the plot requires otherwise. Why even worry all that much if eventually they’ll all be the same and there will be nobody left for them to feed on? You’re telling me Dong Hyun, who was surrounded by at least a dozen of them, didn’t even die but just came out infected from presumably getting attacked by all of them at the same time?

Finally I get what they were going with regarding the residents (btw even with the excuse they gave, there should have been a lot more residents in that building), but too much time was spent on them and I just wanted more SB/YH relationship exploration. It still turned out pretty satisfying overall, but I went in excited about the contract marriage aspect and then I eventually got very bored of the residents. Why did we spend so much time on the old lady only for her to not appear at all as the show went on?
They were often stupid to an absurd level. Yes, in crises the ugly, and often short-sighted side of people comes out, but these people went beyond that. Who sides with a serial killer against the two people who have shown themselves most capable of handling disaster? I was close to dropping it, but by episode 10 I found myself interested again. Even with only 12 episodes this show sorta dragged.

Still, it had great acting, was wildly funny at certain points, had two likable leads even if they did annoy me, and overall was pretty entertaining. I just don’t think it’s a masterpiece by any means, as I’ve seen a few people claim.