The story begins when Banban Akaza arrives on Earth to the city of Megalopolis. He is transferred to the S.P.D. (Special Police Dekaranger) Earth branch by his commander. By that time, Agent Abrella, an Alienizer arms dealer, turns his destructive attention to Earth, helping the criminals there. It's up to the Dekarangers to stop them and bring them to justice. The SPD of Earth are stationed in the Deka Base under the command of Doggy Cruger.