I think this is one of the best psychological anime I have seen till date.
As many reviews suggest, one must not miss this anime and cannot resist to watch it in one go!
Story: Very unique and gradually upgrades to high tension levels with brilliance
Art: Music is apt and depicts the situation properly
Character: What makes this anime unique, smart and brilliant are the characters who are very well made according to story and can never be forgotten.
Enjoyment: As it unique, definitely enjoyable
Overall: Don't think anything, just watch this anime and you will definitely love it.