As of the 2008 series reboot, Casshern SINS, Casshern is a robot living in a post apocalyptic world where humans have almost died out, and robots are slowly dying from a mysterious disease. Casshern is immortal, can recover from all injuries, and goes berserk when antagonized. He has forgotten all of his memories and is mysteriously persured by many robotic foes.
In the series Casshern is hunted for killing a robot girl named Luna, who supposedly gave robots eternal life. Casshern begins to meet up with robots from his past, one of Luna's guards, two robots that helped him kill Luna, the robot that created him, and the one that ordered his creation.