I’ll start by saying that the production is very good, but it’s not a surprise as there is nothing less to expect from Netflix. All the actors did a great job.
They tried hard to come up with a fresh story about zombies. In brief, the drama Is the typical survival race against zombies with a mix of gore & korean school issues such as bullying, teen sex, etc.

From the origin to the virus to the end with Nam-ra & “others like her”, it is poorly explained and doesn’t really make sense.
The drama could have been good, but unfortunately, It is overall a disappointment. The characters aren’t developed and it became a succession of unfortunate events, of useless fights between the characters, of human beings at their lowest points, etc. It feels they tried so hard to go against cliches that they just made the worst happened to “surprise” you.
Some characters & scenes are useless to the story & it feels that some scenes were added to add length to the story but definitely failed to add depth. The teenager who had a baby. On-Jo’s father who spent 10 episodes to look for, but died after 1,5 min he reunited with her, The bully that stays alive (but we don’t know how) & spent all episodes to run after ML to finally gauge his eye out and died with him. Etc, etc...

It reminded me a lot #Alive but with schoolmates rather than neighbours. The drama format was issueless and they could have made a movie out of this story, it would have probably avoided all the unnecessary added scenes.