In a distant future, Earth has turned into a wasteland, and humanity as we know it has perished. The only survivors are sentient robots. They were meant to live forever—until the one known as Luna died, triggering the Ruin. Their bodies are now rusting, and there is no way to repair the damage. Now, the robots are left to ponder their own mortality, sustained only by the rumor that consuming the one called Casshern will grant them immortality. Casshern knows nothing of his past, his purpose, or his true nature, but he must uncover the truth, or he will endure the relentless torment of being hunted by robots desperate to avoid death. Casshern leaves death in his wake, yet he must confront it to discover the reality of this world.