Jûzô Saejima holds the position of Metropolitan Police Department Superintendent General and founded the Brave Police Project. He worked directly with Chief Engineer Toudou to create the first robot, Deckerd. When Deckerd gained self-awareness and formed a bond with a young boy named Yuuta, Saejima personally revised police regulations. This unprecedented change enabled Yuuta's appointment as a police inspector despite his youth. Saejima then commanded the Brave Police Division, issuing their operational orders and acting as their primary liaison within the larger police structure. His strong advocacy regularly brought him into conflict with Vice-Commissioner Azuma, a leading opponent of the project.

Saejima displays a flamboyant and enthusiastic personality, frequently emphasizing elements he considers "cool." This preference occasionally shapes operational procedures, such as requiring vocal commands for robot combinations or demanding aesthetic additions like a tiger head emblem for the Build Team's combined form. He remains deeply committed to his profession and focused on advancing innovation in law enforcement.

Personally unmarried at 45, his lifestyle is noted as a reflection of his character. His household includes three servant robots: King Kizer, God Bomber, and Ultra Diver. Saejima also originated the names for several Brave Police robots, specifically Build Tiger, Super Build Tiger, J-Decker, and Fire J-Decker.

Beyond command duties, Saejima engages directly in crisis management alongside the Brave Police team during major threats. He exhibits adaptable leadership, skillfully navigating bureaucratic hurdles while championing the unit's operational independence. His ongoing professional friction with Vice-Commissioner Azuma stems from fundamentally differing philosophies on integrating advanced technology into police work.