This is not an easy manga to read and to review.
A big part me was completely disgusted and disturbed by everything that was going on, but another part me was fixated, looking into the eyes of the darkness that's consumed these people.
While the story itself was not that bad, I think that it would have been much better -as well as easier to buy- with more mature characters, instead of high-schoolers in the middle of their high school drama.
As for the theme of the manga: it's all about obsessions; that's the main driving force behind most of the characters' actions. The characters themselves think that what they feel towards each other is love when they're only obsessed beyond the point of recovery.
I loved the art, especially the way the mangaka drew Tatewaki's horrific expressions. I swear I got goosebumps all over.
Overall: disturbing, disturbing, disturbing. Only read if you can handle some of the most distasteful, fallible characters.