In the year 2025, the world population has exploded to over 10 billion. In search of a new place to live, mankind initiates a space exploration program entitled the Mars Terraforming Project. Slowly, mankind successfully transforms Mars into a habitable planet. But, when a Japanese spaceship returning from Mars crashes onto the streets of Tokyo, a giant, vicious monster- Negadon- is unleashed. Only Dr. Narasaki and his long-abandoned robot Miroku can save Earth and mankind.