Hideki, often called by his nickname Hakase, is a member of the UFO Kids Corps who joins the team as the fifth and final member. His journey begins with tragedy when he loses his father during a battle between Dai Apolon and the Dazarn forces. His father, who was the chief planner of the Akabe Dam project, had planned a trip to Tokyo with Hideki to report on the dam’s near-completion, but perished in the conflict. Following this loss, Hideki becomes an orphan and is sent to live at the Aozora Gakuen, also known as the Blue Sky Orphanage.

On the day he is scheduled to leave for the Akabe Dam site, Hideki disappears and is found by Takeshi crying in the forest, who persuades him to continue the journey. En route to the dam, Hideki witnesses Takeshi transform to confront an attacking monster. He aids in the battle by using his quick thinking to direct UFOs to reflect sunlight onto Dai Apolon, providing the power needed to overcome the threat. This action impresses Takeshi and leads to Hideki being invited to join the group.

Within the team, Hideki stands out as the most intelligent member, openly displaying a wealth of knowledge and talent that leads him to serve as the group's strategist. He is characterized as a logical thinker who typically prevents emotions from clouding his judgment, a trait that can sometimes border on arrogance despite his fundamentally good intentions. In addition to his strategic mind, Hideki is also an invention enthusiast, showing a particular talent for building and tinkering with machines, such as creating a pendant-type transmitter. He can become emotional or upset when his inventions are mocked or not taken seriously. His uniform within the UFO Kids Corps bears the number 99.