None of my favorite pieces of media are perfect. Some of them get close, but this manga series is not one of them.

The review below this line has manga spoilers, so if you haven't finished, let me just say: enjoy it!

I rated it 10 stars, not because it was technically great, but because of how I just thoroughly enjoyed it. Here, I'm giving it a 9/10. If I were to break this down technically, I'd call this story an average plot that was elevated by the art to an 8/10 experience. It's nothing special, hindered a lot by the main character being a brick and not really changing in the slightest.
For a quick run-down: (keep in mind that at the time I'm finishing this review, the only manga I've read is Demon Slayer/Kimetsu no Yaiba and Haikyuu! before reading this)

Story: 7/10
A very interesting world that didn't quite live up to the hype of the first arc. The premise was very interesting and the story fell within a lot of regular storytelling bounds that we could have probably all seen coming (apart from maybe two sections: Peter Ratri's death and the finale).
Though you would probably label the message of looking past our differences as cheesy, I really liked how this story turned something purely fantasy into something that is very prevalent. I'm not going to give it social justice brownie points or anything, but as something that is so mainstream the page about wondering how we would treat each other differently under different circumstances really recontextualized this series' themes in a way that completely swept me off my feet.

Art: 10/10
This manga would not have been nearly as breathtaking, convincing, or terrifying if Posuka Demizu had not just absolutely blown us away with their art. Every scene of this story sells what it needs to: suspense, terror, loss, fear, everything. This world is one that I can imagine quite clearly all thanks to the beautiful artwork.

Character: 8/10
Norman and Ray are tied for best character in the entire manga. Isabella is a close second, followed by Yugo.
I absolutely adore Ray as a character. I found him interesting from the very beginning of the anime all the way to the end. Actually, especially at the end. On one hand, it would have been nice plotwise to have him and possibly Norman die and see Emma take on the character development of having her two closest friends die. And for a while after he was planned to die, Ray really didn't serve a good purpose. It was not necessary, but I'm very glad that he was alive to solidify the end of Isabella's arc. Seeing how they were somewhat the same in their silence and how guilty they both were was awesome and very enjoyable.
I was genuinely not expecting most of what happened with Norman in this series, except for the fact that he wasn't going to die. The fact that he became an antagonist and then was on their side somewhat seemed to follow Isabella, which I thought was pretty cool, whether intentional or not. Norman is my least favorite character personally, but he continually surprised me thematically.
The only thing that really weighs on this whole series is the character of Emma. She is not interesting and never becomes interesting. I understand that main protagonists are usually not as diverse in their character arcs because they are the face of the story as well as needing to carry the plot, but every time she does something, she forgets it immediately. She goes through no change after the first episode. She's perfect from the beginning. It would have been nice to see permanent change in her, even as small as being more cautious after the first deaths in the series, or maybe having Yugo be a bigger part in her decisionmaking. However, the thriller-type storytelling does hinder this, and this story is not trying to be something new and interesting. It would have been nice, though.

Enjoyment: 10/10
I adore Ray and Norman. I loved Yugo's character. The slow reveal of everything, the tension, the friendship between Mujika and Emma, Peter Ratri's end, Emma's sacrifice, and all the way back to the beginning, with the tiny kids wondering what was beyond the gates outside of Grace Field. Since you're with all these characters for so long, you don't realize how much they've grown.
No matter my technical complaints, all the things that could have been changed, all the ways I would have liked the story to be more impactful, this story still managed to keep me on my toes the entire time. I thoroughly enjoyed everything about this world and its characters. As a I writer, I relished in the ending being bittersweet (but as a reader, I was completely destroyed). This series is very strong, and will leave a mark on how I write and how I think about the world.

Overall, I don't really care what people think about this. It's mainstream, it's cheesy, it has problems, and it has a pretty uninteresting main character. None of those things are going to take away from how much I adored this manga. The bests of this series are my favorite things in all of the media I've ever consumed, and if people say that there are things that are much better than this, it only makes me excited to dive into more worlds that will hopefully have as much of an impact as this series did on me.