It seems like I am going to be a lot nicer to the second season of this show than many others have been. A big issue people had with it was the anime skipped one of the arcs of the original manga. That said I read into it and realized that to be honest, it doesn't sound like that arc was really important to the story at large. Even reading about the events that happened, doesn't add any missing context to the anime. You still have a complete story going in.
That said, the story on its own has some issues. For those who haven't watched it, you can honestly enjoy Season One as a stand-alone story and I strongly recommend it. I will be going forward with this review under the assumption you have seen the original.
I know I said I'll be nicer to this show than most, and that's true, but I'll get the problems it does have out of the way first. The biggest one is that this feels rushed. I'll point out one example, and that is an escapee of the Grace Fields farm having a deep-seated hatred of demons because of what happened to her and is blinded by the idea of revenge. This is a character flaw that is pretty much-taken care of in one scene later on in the show, with nothing of note happening with her in between that scene and her introduction. This is a running flaw in the show.
The second thing being the show just doesn't have the same tension and terror of the first season. The demons were horrible by and large because of how little was known about them. Now that the kids are in the outside world, there isn't much of a choice but to start sharing more about society at large. With the demons being demystified, even the terrible things the kids have to deal with lose a bit of their intensity. The demons just stop feeling nearly as terrifying.
All that said, the show is largely carried because you go into it caring about these characters. Emma's desire to save everyone is continually tested, especially when the safety of the demons becomes an element of the story. There is a big question asked for these kids, is it okay to kill the demons to keep the humans alive? It's a pretty simple question, and it's something that most of us already have an answer to anyway. Where the show succeeds is because we care about Emma and the others. We know what she suffered through in the Grace Field Farm, and by extension, we know what others had gone through to a certain degree. Even if the outcome is obvious because we have such a connection to these characters it doesn't matter if you see part of the ending coming.
The show even carries a big strength it had from the first season, and that is these all still feel like children. For all their hardships, their strength, and their intellect, the show never forgets we are dealing with kids here. They are emotional, they have fragile emotions, they are often confused as to what should be done. It does a lot to make the emotional impact of what happens really stick, even if the narrative feels rushed.
There is no getting around there being aspects of the show feeling like they were put in and forgotten and the plot feeling rushed. These are big enough issues I can see why people walked away from this season upset. But in the end, I still think it was a really good show, even if it doesn't live up to the first season. The animation and characters are fantastic, and it does a pretty good job at conveying its themes and making you care about the plight of the characters. It's a good note to go out on for a show.