Deadman Wonderland

This Anime is so underrated! 

I love it and it's now on my top 5 list. :3

Deadman Wonderland is a prison, more like a circus on the outside, entertaining the people around the once was Tokyo. Tokyo was demolished by the strange Red Hole that transformed some people into Deadmen, using the Branches of Sin (aka their blood) as weapons in a deadly deathmatch.

The main character is Ganta, a 14 year old boy, who after a massacre of his entire class gets falsely accused and put into the prison.

Story goes that Ganta battles others with the blood power, meeting new friends and discovering Shiro, his new best friend.

This Anime is so good and believe me if you enjoy ones like Death Note and Elfen Lied you will definitely enjoy this!