I have watched the anime version of this and completely loved it.
The series is a bit different from the movie. In this movie it still is gory and such but there are a few things that has been change probably to make it more cinematic.
So I just recently realized that the main character of this was played by Kento Yamazaki (he played L as well on Death Note). PS: It’s quite obvious now that I do not research what I watch, I just watch it. Not anymore though.
I loved the concept of the story even before when I watched it as an Anime. It was mysterious and it really makes one think.
You can watch it here.
It was rated 6.2/10 by IMDB, a bit low I must say (but I really can’t understand how they rate it), see it here.
I recommend this to those who loves mystery.