Goro Makiba is the son of Danbei Makiba and younger brother of Hikaru Makiba. He lives and works at the Makiba Ranch, managed by his father, who considers Goro's contributions essential, even calling him the "father of the Ranch" due to his diligence despite his youth.

Goro displays childlike enthusiasm and is easily impressed, especially by Koji Kabuto's piloting skills, aspiring to be like Koji someday. His personality is marked by a strong work ethic and dedication to ranch duties. Physically, he is an average-height child with black hair and eyes. His attire features a Western-inspired style: a white shirt with red stripes, a blue vest, jeans, a yellow scarf with green polka dots, and sometimes a brown ten-gallon hat.

A significant story arc sees Goro befriend a Vegan infiltrator using the alias "Haruo," posing as a student at Goro's school. This infiltrator is later revealed to be Hulk, a member of the Vegan Empire. Goro experiences deep distress upon discovering Haruo's true identity and allegiance, particularly when Duke Fleed confronts and destroys Hulk. This event profoundly impacts Goro, leading him to fully commit his support to Duke and Earth's defense against the Vegan Empire.