This is one of the best mangas I read in a while. I enterd this expecting... Well, surely not expecting this.
I don't want to spoil anything but if you like in depth characterization and genius writing of heavy themes you'll like this.
Story is an 8 I'd say. It is fairly original but nothing too special. Although it is the perfect setting to reveal the psychological drama and turmoil in the characters.
The art is ok. I'll give it a 6 although I did not enjoy it that much. You don't mind the art as the manga pulls you in and doesn't let you
Characters... outstandingly fleshed out. A perfect ten. You'll see their thoughts, their feelings and weaknesses and small strenghts they have in them. 10/10
Overall it's not a perfect ten(because of the art mostly) but I'd give it a 9.9 if I could. I'm gonna read it again some time for sure