Go Nagai is a noted manga artist known for his revolutionary works such as Devilman and Mazinger Z. In Getter Robo, he is the original designer for the eponymous robot which was later used by his assistant Ken Ishikawa for a manga he created which gave his mentor the honor of the being the series co-creator.
Go Nagai once worked under the famed Shotaro Ishinomori as an assistant. With the success of his Harenchi Gakuen manga, despite its controversy Nagai moved on to other works including one-shot gag manga and another notable manga called Abashiri Family. He later founded Dynamic Productions to manage relationships with other companies regarding his works. It was there that his most famous franchises: Devilman, Mazinger, and Cutey Honey were developed. It was also when he reencountered Ken Ishikawa after he went out on his own. Nagai hired him as another worker at his company.
While the story of Getter Robo and its characters were the products of Ishikawa; as stated previously, Nagai was the original creator of the eponymous Getter Robo back when it was a design idea for Mazinger Z. Ishikawa found the draft and with Nagai's permission and help redesigned the robot to create the Getter Robo. As the robot is the centerpiece of the franchise, Ishikawa credited Nagai with its creation and his mentor as the co-creator of his original manga. As such, it is classified as a property of Dynamic Productions while Ishikawa was in charge of the series until his death in 2006. After Ishikawa's death, Go Nagai and the rest of Dynamic Productions would continue to use the Getter Robo franchise in their works. Nagai himself created crossover manga with the Getter Robo cast in short manga that involved the characters from Devilman and Demon Lord Dante.