In the year Universal Century 0079, humans have colonized the area of space lying in between the Earth and the moon. However, the ambitious Zabi family, rulers of the Duchy of Zeon, the grouping of colonies furthest from the earth, has sparked a war.
Officers Tsujimoto and Kobayakawa are transferred back to Bokuto Police Station after stints in other police departments. Shortly after this, the discovery of smuggled firearms and the recovery of a magnetic disc herald new troubles for Bokuto station as the Chief is thrown in jail for keeping silent over "Bee Number One", developed by Detective Emoto who went missing two years ago.
Earth is invaded by the criminal organization known as Makuu, led by Don Horror, who had first destroyed a space colony near Earth. Don Horror wants to dominate the whole universe, and the Earth represents an obstacle that he has to overcome by turning it into a domain for all evil. In response to Makuu's attack, Space Sheriff Gavan of the Galaxy Federal Police is deployed to Earth to defend his mother's home world.
