Well the Art is not bad (but not really outstanding). But ...
The "story" is big BS, period.
Everything depends on dumb & made-up coincidences, pure violence, sadism and totally perverted understanding what is allowed in society aaaand a little bit of school romance. Some incidents in this manga are justified in such stupid way, that i thought that the mangaka tried to insult my reasoning personal.
Some thoughts on genres and categories: It's IMHO more shounen than seinen. There is no harem, maybe a reverse harem whit the male slaves and their main female warden. And the perverts are whiteout a doubt the girls, almost all of them. And this hardly a comedy, the most comedy scenes in this manga are when somebody is beaten up bloody whit a riot stick (this happens all the time). Let's do this in real life and how funny this turn out to be. In real life a riot stick (the telescopic variant) is deadly, using fists and kicks is bad but a riot stick is over-the-top.
This manga favors more "realistic" faces over some "shounen" faces when it come to facial expressions. This gives the manga the more adult touch. My problem is that the teenagers and kids, which read this manga, learn through this manga that to use violence and being sadistic is really OK. As the comments here shows some teenagers think this is even a "hilarious comedy". Yes, some singular events in this manga could be seen funny IF there were standing alone, but these events aren't singular, there are part of a setting/plot which is disgusting.
I downloaded first and read second. Which was very wrong. So i skipped though the chapters to see if my first impression after volume 1 was wrong. And my first impression wasn't wrong. This manga is a waste of time AND disgusting.
Do not read this, there are a lot of good manga out there.