Julie Kokematsu serves as a primary henchman for Princess Mirenjo within the Sukapura Dynasty faction. He possesses distinctive features including bushy eyebrows, a long nose, and a prominent bucktooth. His standard uniform comprises a pink jacket with cyan collar lining, a black shirt featuring a skull-like print, pink pants, and a helmet equipped with three multicolored lights functioning as an emotional indicator—red for lying, greenish-blue for fear, and yellow when having an idea. Out of uniform, he typically wears a dark khaki jacket over a yellow sweater, dark pants, and a driver's cap, revealing a bowl-cut hairstyle when uncovered.

Julie exhibits a lecherous nature, frequently flirting with women such as Mirenjo, Karen, and Tina Yesterday. Unlike previous "brain" members in similar roles, he lacks mechanical aptitude and cannot build mechs himself, instead using a remote control to summon supply boxes that automatically assemble into combat machines. He occasionally displays volatile behavior, brandishing weapons like guns in exaggerated but ultimately harmless outbursts.

Within the core conflict, Julie assists Mirenjo and Prince Komaro in their quest across different time periods to locate the mythical Firebird (or Cosmo Peacock) to secure rulership of the future Kingdom of Fir or Calendar. He operates alongside fellow minion Alan Sukadon and receives occasional support from the infatuated Count Donfanfan, whose romantic pursuit of Mirenjo sparks jealousy and dismay in Julie.

A late narrative revelation discloses that Julie and Daigoron (Princess Karen's robotic guardian) were secretly sent by the Dalla hermit to monitor both factions' progress and determine worthiness for the throne. Despite this hidden mission, Julie's feelings for Mirenjo were genuine. Following the kingdom's destruction, they shared a passionate embrace before parting ways to unknown destinations in time.

Julie reappeared in the crossover special *Time Bokan: Royal Revival* as a participant in a race among various franchise villains, indicating his survival beyond the original series. Preliminary design concepts for the series initially depicted him with a more conventional appearance similar to predecessors before finalizing his unique look.