Plot - the plot is written with some very tiny loopholes but its interesting enough to keep you engrossed into the drama. Starting from the post covid era to a sudden outbreak that could not be contained within the building, they make a lot of parallels with covid and this virus. Even though both are different in many ways, human survival instincts acts up in both cases.

Characters - you could see how humane they were. (except for the occasional psychos.) but yes, no matter how annoying you found they residents, each and every one of them were humans who got desperate and went crazy when the situation turn to kill or die.
We had characters of all sorts living with all sorts of people. The infected themselves being made to feel human and giving them time to regain their humanity to the point that by the end we were left with infected people who could control their thrist very well.

Main Characters - Both of them. I love Them. Where Sae beom hestitated, Yi Hyun backed her up and vice-versa. No lovey dovey in the middle of crisis like bloodbath and theyre kissing, no. They kept their cool, they found ways out.
I also love how Yi Hyun gets infected at the end and we see him struggling, how even though he could control himself, he let himself bite the villain AND threw up the blood right after.

A Scene I Will Forever Remember - When Yi Hyun smears blood on Oh Ju Hyung's face and watches him scream. It was real. The most realistic expression of desperation.
Say during covid - when people were going out without masks, it made me crazy. It made me crazy that people i know were dying, were struggling and they had no remorse walking around. I wanted them to feel what I was feeling.

All in all, Genius. Amazing. Probably one of the best potrayals.