The universe has come together where aliens from many different planets coincide in peace. Banban Akaza was transferred to the Earth branch of S.P.D. (Special Police Dekaranger) in the city of Megalopolis by his commander. By that time, a major outbreak of crimes had broken out by a group of aliens known as the Alienizers. Agent Abrella, an Alienizer arms dealer, turns his destructive attention to Earth by helping the criminals there. It's up to the Dekarangers to stop them and bring them to justice.
