A survivor of the devastating magnitude 11.4 earthquake that sunk 75% of Tokyo (which he has no memories of), middle school student Ganta Igarashi lives an ordinary and peaceful life — until the day a mysterious man in blood-soaked crimson armor comes into Ganta's school, slaughters his entire class, and implants a strange red crystal on his chest. Ganta becomes the only suspect in the slayings; even though he proclaims his innocence, the court convicts Ganta and sentences him to life imprisonment at Deadman Wonderland, a privately-owned penal facility (the only one in Japan) disguised as a theme park to attract tourists.
While serving his sentence, Ganta befriends Shiro, a strange albino girl who knew Ganta as a child, and discovers the truth about Deadman Wonderland: the facility houses "Deadmen" — people endowed with an ability to turn their own blood into a weapon (the "Branches of Sin") — and the sadistic proprietors of the prison force the Deadmen to fight each other to keep them occupied…and to entertain the tourists willing to pay large sums of money to watch them fight.
As the days drag on, Ganta — who finds himself as the Only Sane Man amongst the Deadmen — finds himself forced to make a choice: he can either lose whatever remains of his sanity or learn to stand up for himself.
Thus goes the tale of Deadman Wonderland, a monthly Shōnen manga written by Jinsei Kataoka and illustrated by Kazuma Kondou (who both worked on the Eureka Seven manga). The manga received an anime adaptation from Manglobe in the Spring 2011 season, and Crunchyroll simulcast the series (with English subtitles) an hour after broadcast in Japan. FUNimation licensed the anime in the US and Canada, and its dubbed version premiered on Cartoon Network/[adult swim]'s Toonami block on 26 May 2012.
I'll be honest I never heard about it before Toonami. I liked it, it's not the sort of thing I usualy watch but it was a fun little series. Sucks that it stopped right when the plot was getting good though.