Dr. Kozaburou Nanbu is a high-ranking executive within Interpol and a prominent member of the International Science Organization, the global body dedicated to combating the terrorist activities of Galactor. A scientist of considerable repute, his expertise spans numerous fields including space engineering, physics, chemistry, astronomy, and medicine. He is also the creator of the Science Ninja Technique, the specialized martial art employed by the Science Ninja Team, and is the architect behind much of their advanced technology.

Nanbu is characterized by a calm, collected, and analytical demeanor. He is a strategic thinker who consistently encourages the team to approach their battles against Galactor with creativity and outside-the-box solutions. While he maintains a professional and reserved exterior, rarely displaying strong emotions openly, he harbors a deep sense of loyalty and a powerful drive for justice. He often couches his protective actions toward the young team members in professional or logical justifications, preferring to avoid open displays of his genuine care for them.

His primary motivation is the protection of Earth from the conquest efforts of Galactor. To this end, he formed and commands the Science Ninja Team, a small, elite unit of five young pilots, trusting in their abilities and loyalty regardless of their personal histories. In his role as the team's commander, Nanbu is responsible for deploying them on missions, designing and upgrading their primary spacecraft such as the God Phoenix, and overseeing operations from a crescent-shaped coral reef base. A key design feature of the God Phoenix required the cooperation of all five team members to activate its primary weapons, a measure intended to foster their teamwork. While he has the authority to deploy Interpol troops or other assets like the Red Impulse squadron, he generally reserves direct combat for his Science Ninja Team.

Nanbu's relationship with the five members of the Science Ninja Team is complex and deeply paternal, though he rarely frames it as such. He became the legal guardian for four of them after they were orphaned. He took in Ken Washio at the request of Ken's father, the mysterious pilot Red Impulse, and raised Joe Asakura in secret after faking the boy's death to protect him from Galactor assassins. He also provided a home and a base of operations for Jun and her younger brother Jinpei, setting up the Snack Bar J as a cover for the team's meetings. The fifth member, Ryu Nakanishi, was not raised by Nanbu as he still had a family, but Nanbu has demonstrated a fierce commitment to his safety nonetheless. Beyond the team, Nanbu shares a long history with the commander of Red Impulse, who was a childhood friend. This friendship led to his role as guardian to Ken, whose true parentage Nanbu kept secret for years to protect the father's undercover work. He also has a professional relationship with Director Anderson of the International Science Organization, whose position he ultimately assumes.

During the events of Gatchaman II, Nanbu continues to lead the fight against Galactor. A culminating point in his development within this series is his ascension to a higher leadership role. Following the death of Director Anderson, Dr. Nanbu takes over his position at the head of the International Science Organization, marking a significant expansion of his authority and responsibility beyond the direct command of the Science Ninja Team.

Among his most notable abilities are his exceptional intellect and scientific genius, which are crucial for developing the team's weaponry and countermeasures against the sophisticated mecha deployed by their enemies. He holds degrees from prestigious universities such as Oxford and Cambridge. Beyond his scientific prowess, he is also a shrewd strategist and a capable administrator within the complex political landscape of the ISO and Interpol, skills that are essential for securing resources and maintaining the covert operations of his team.