Casshern Sins (2008)

With Luna dead, the robot civilization that governs the world begins to corrode, its metal heart rotting from within. Despair cascades across the land, a plague of decay known only as "The Ruin." Casshern, the assassin who struck her down, remains untouched by the blight. Haunted by fractured memories, he can't be certain he truly committed this unforgivable crime. Driven by guilt and confusion, he sets out across the dying world, searching for the truth that binds him, Luna, and the spreading devastation together.