It is the near future, in the 100th year of Showa (year 2025). The population of world is more than 10 billion, and a world-class space development project called "Mars Terraforming Project" is in process. One day, a spaceship "Izanami" crashes in Japan on the way from Mars, and it revives the monster Negadon, which was captured by the spaceship. Can the human race knock down the monster !? Under the desperate situation, a middle age man Ryuichi Narasaki rises up against the monster. He is a robotics expert who lost his daughter in an accident during his experiments. Now, the desperate struggle between Narasaki and Negadon begins!!

In 2047, an unknown, alien lifeform descends upon the Earth, destroying all the major cities in one fell swoop. The survivors unite and build a Diffusor to stop the Februus, the invaders the military would later codename the FOS, and a temporary peace is achieved. Jump forward to 2053, the present. A last, desperate counterattack is being mounted against the enemy. Hiroshi Akishima, soldier in the Planetary Defense Forces Alliance, would like nothing better than a shot at the aliens responsible for his father's death six years ago. However, the new offensive requires the Diffusor to be dropped, leaving the entire planet terribly vulnerable once more. Will humanity regain the stars or lose everything in the final, ultimate gamble?