In the year 2025, the world population has exploded to over 10 billion. In search for a new place to live, mankind initiates a space exploration program entitled the Mars Terra-forming Project. Step by step, mankind successfully transforms Mars into a habitable planet. But when a Japanese spaceship returning from Mars crashes on 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.