I haven't read many manga but this one is certainly one of the best.
It is very enjoyable and suspenseful.

Story: 8/10
The story seems simple, A boy gets sent to prison for a crime he didn't commit and a zombie attack hits the prison and he has to survive as well with the other inmates. What I liked about the story was that the zombies had different species and looked different than your average zombie to make it more interesting. It was very suspenseful and at times you don't know what's going to happen.

Art: 9/10
The art was great. The zombies were really gory and realistic looking which I liked and the character designs were nice as well.

Character: 8/10
You've got your average characters that you see in other manga/anime. The pussy, the badass,the smart one, and cocky guy. The thing I liked about the characters was that it showed their personalities and their past to know them better. Even some of the supporting characters had some development. But overall the characters were decent but not the best.

Enjoyment: 10/10
I really enjoyed this manga. I would stay up late reading this just to find out what happens on the next chapter. The zombies and characters were really interesting. Not all may like it but at least give it a try.

Overall: 10/10
Their may be some flaws of this manga but I really enjoyed it and that is all that matters. I really recommend it to people who like the horror/psychological genre. I hope you enjoy it as much as I did.