Characters barely grow or change over the course of the entire story and when certain characters die they gloss over it almost immediately.
Themes, ideas and concepts aren't explored to their potential, they are forgotten about or prematurely dropped.
After the first arc the pacing is all over the place. The story felt rushed and it seemed like the creators didn't have a set plan for the whole story, its universe or its characters. The comic book needed to go a pre-production phase where they could've tied the story together from the beginning and then it should've gone through several revisions.
The biggest sin in my opinion is that the creators opt to tell instead of show the reader, they completely skip important events only to bring it up later with some lazy exposition or a one page flashback. Characters become masters in a certain field in just a single page and the use of time skips are frequent, we barely follow their "growth" it just suddenly happens.
Overall the comic book is okay and the best thing about it is the art. If the story had been better, the characters had some substance to them and they continued to explore some of the darker themes this manga would've become a classic.
