I will start by saying that I don't think manga is for me unless it is very linear. I found this one a bit hard to follow and the story jumped around too much for my poor brain to handle. The story is interesting, and I appreciate that it is a good manga. Which is why I gave it a 3 star, because I probably would have given lower if I was rating it as just a read for me. And I'm sure that someone who enjoys manga would give it a higher score in many instances. So, 3 seemed to be a safe bet. My son loves the series and I really read it to make sure that it wasn't going to get into some of the territory of other manga which can be a bit too MA for his age group.
So far, after the first three volumes, I consider it among the "safer" manga for younger kids. Still violent but not as much of the other elements I find a bit more disturbing.