When you start reading this manga, you'll probably think "Wow, this universe is awesome! There's so much to explore in this world setting! And at this pace, how come the story ends so quickly?".
That I've asked myself many times while reading this, while constantly wondering about the chapter count. I was trying hard not to be dissuaded by my intuition and enjoy the story in spite of what I was worried about, because the art is fantastic and the premise seems interesting.
Here's something: there's not emotional development or insight into the personality of the characters. It seems like their persona is simply made out to be to represent some conviction or be some sort of vague representation of their power.
You'll bump into a lot of scenes from cool moments in fights and dangerous situations they will eventually face, but there's not much behind it. You'll occasionally see two characters made to get along with each other and maybe develop some mutual feelings, but it won't be consumed.
When a character dies, there's nothing left of him remaining in the story, like [spoiler reference 1].
There's not enough background or to justify why a character behaves the way it does.
There are some characters who just exist for the sake of being a power piece somewhere along the line and then vanish into nothing, like the [spoiler reference 2]. Flusterings and feelings that may appear will seem to be simply for the sake of flavor and fan-service, not because it actually means anything.
I've struggled to finish this series, not because the story kept getting duller (it already is pretty dull), but because the characters felt so bothersomely shallow. I thought about dropping Area D many times because I felt no reason to continue reading other than to know how the characters would end up being. As expected, the ending is premature. THERE ARE A LOT OF THINGS LEFT UNANSWERED OR UNDERDEVELOPED.
I'll try to save you of your possible worries and anxiousness: if you're an emotional person, don't pick up this title. You'll find really hard to become attached to what's going on because there's not enough juice, not in the story, not in the interactions with the word, and especially not in the characters.
If you just want to see some powers flying around in a different world setting, then go for it. As I mentioned, the art is really cool.
*SPOILER REFERENCES*
[1] - Tatara or Owl Eyes
[2] - Sol/Luna sisters
