After defeating a group of robots in battle at an abandoned amusement park, a human resistance fighter slips inside Castle Promise, a massive robot-manufacturing facility. Luna Kozuki plans a revolt with the human workers; that night she sees Lucky and her old lover, Tetsuya Azuma. The next day, the rebels are betrayed by a fellow prisoner who was promised freedom; the collaborator is killed and Luna is captured. Akubon plans to publicly execute her as if she were Casshan, to break the people's spirit. However, the real Casshan saves Luna and kills Akubon, though the Black King escapes.
Far in the future, ecological disaster on Earth led humans to create a race of androids called Neoroids to clean up the mess but they promptly turned on their human masters and enslaved them. Enter a lone fighter named Casshan with a mission to free humanity ... and restore his family's honor.
