Dr. Kozaburo Nanbu is a central figure in the Science Ninja Team Gatchaman series, serving as the brilliant and determined founder and commander of the elite Gatchaman team. His background reveals a man of extraordinary intellect and resources. He was born into considerable wealth, as his father was a powerful businessman who owned an airport and a bank, providing Nanbu with the financial means to pursue his ambitious scientific goals independently. His academic credentials are world-class; he graduated with top honors from both Oxford and Cambridge Universities, with areas of expertise spanning aerodynamics, mechanical engineering, bioengineering, and computer engineering. He also holds the position of Professor Emeritus at the University of Tokyo and serves as a consultant for the International Science Organization's significant Mantle Plan.

Personality-wise, Dr. Nanbu is consistently portrayed as a calm and collected individual who rarely displays strong emotions openly. Despite this reserved demeanor, he possesses a powerful sense of justice and a deep, fatherly care for the young team members he has recruited and raised. He is a pragmatic and demanding superior, often clashing with the hot-headed leader Ken Washio over mission tactics and the need to prioritize the mission over personal feelings. However, this strictness is balanced by a thoughtful side, such as personally remembering and celebrating the birthday of the youngest member, Jinpei, when the others had forgotten. His primary motivation is the protection of Earth from the secret society known as Galactor, a threat he foresaw and began preparing for long before the world's governments understood the danger. He is willing to sacrifice his own safety, and make difficult decisions, for the sake of future generations.

In the story, Dr. Nanbu acts as the team's strategic leader, technical developer, and emotional anchor. Operating from his base, he analyzes Galactor's movements, develops the team's advanced weaponry and vehicles like the God Phoenix, and issues mission orders. His role expands over time, as he eventually takes over leadership of the International Science Organization after the death of Director Anderson in the sequel series Gatchaman II. His key relationships are primarily with the five members of the Gatchaman team, most of whom are orphans he personally raised, making him a paternal figure in their lives. He has a particularly complex relationship with Ken Washio, whose father, Kentaro, was Nanbu's close friend. To enable Kentaro to act as a spy within Galactor under the identity of Red Impulse, Nanbu hid the truth of his survival from Ken for years, creating significant emotional tension. He also rescued Joe Asakura after Galactor assassinated his parents, giving Joe a new purpose and identity.

Throughout the series, Dr. Nanbu undergoes significant development, particularly in his portrayal as a man of action. While initially depicted as a non-combatant commander, later episodes reveal him to be surprisingly capable in the field, displaying incredible marksmanship, acrobatic jumping skills, and even engaging in hand-to-hand combat with enemy soldiers. He also demonstrates immense mental fortitude when captured by the enemy leader, Count Egobossler, enduring torture and interrogation only to turn the tables and extract vital information for his team. His development culminates in a heroic and tragic death in Gatchaman Fighter, where he is killed by Egobossler, an event that serves as a profound shock and a major emotional catalyst for the team. Even in death, his legacy continues, leaving behind a mysterious reincarnation device and the team of heroes he created to carry on his fight. His notable abilities extend far beyond his scientific genius; he is a master strategist, a capable political operator who can manipulate funding and resources, and a surprisingly effective field agent with strong combat skills and unbreakable willpower.