Inspector Satsuda is a detective with the Tokyo Metropolitan Police Department. He doggedly pursues Dr. Hiroshi Amano, suspecting him of involvement in a major robbery three years before the series' events, despite lacking conclusive proof. Satsuda's investigative approaches often backfire, inadvertently complicating cases rather than solving them. Yet, he displays authentic bravery and a readiness to aid civilians during crises, especially those instigated by the series' antagonists.

A peculiar pattern surrounds his assigned police car, which frequently vanishes at crucial junctures. Unaware of the truth, Satsuda does not know the vehicle is actually the disguised form and physical vessel for Guard Star, a member of the Universe Security Force. Guard Star's consciousness inhabits the car, compelling it to depart autonomously to join Space Police operations against Draias and Dr. Jango, stranding Satsuda.

Exposure to the true nature of the Amano Peace Science Laboratory and its link to the Space Police catalyzes Satsuda's development. Moving from an obstructing figure, he evolves into a cooperative ally for the heroes. He actively partners with Guard Star to anticipate and thwart bank robberies planned by Draias's minions, even when his human colleagues dismiss his theories.

Physically, Satsuda has no glasses, freckles, mustache, or beard. He is a non-smoker. His skills include holding a 3rd-degree black belt in judo, and his standard-issue sidearm is a Cz75 pistol.