Well where to begin, this story is all over the place. It starts off well at the first episode but then at the second and third I began losing interest, why, thats because 15 minutes of each episode are wasted what happens in that 15 minuted have nothing to do with the story or character development, then around 6-9 a few relevant things happens, its just coming down to the end, the studio tries to tie up everything, this happens in episodes 10-12, they were actually the only part other than the first episode that were enjoyable. You can get the idea that this show was not well presented, there's no flow of the plotline its like a bumpy road. Lots of things are left unexplained, I do beleive that it ended for a second season, given the manner in which it ended, but if they do make one, I hope they don't make a mess like this one.
Noticeably the best part of this show, the fight scenes are bloody the artwork is decent, the character design is good. Given this came out in 2011 it is expected to be good, however the battles tend to be repetitive its the same actions over and over again, which after a while becomes boring and tedious to watch, I was dissapointed since this did come out in 2011 I expected them to at least be dynamic in the battles, I mean there are so much anime that shows how to change the style in battle scenes and its not like its hard to find anime like that, this is a recent show it has a lot of anime to get examples from.
Saya's singing is annoying, fucking annoying, I muted the episode when she started to sing and its not like she does this once, it happens a lot. The soundtracks are well used to suit the scenes to bring feeling into it, but its not anything facinating about it.
Annoying, no emotions, very little development (actually I don't think there was any relevent development to the plot other than Saya regaining her memories). By far this is the worst part of this show.
Horror, mystery and violence are my favourtie categories of anime, this show failed in each and every one of them, its a good thing that this anime is 12 episodes long otherwise I don't think I could have even finished it. I don't think any kind of audience would like this show no matter how much they like anime. Big dissapointment, but there is a good side to this, at least this is not the worst anime out there its still better than a lot of anime out there.