Kyoshiro Nagumo emerges as a key antagonist within the SAGA and SIN story arcs. He takes command of Team AOI, instituting significant organizational shifts and spearheading technological advancements. His leadership introduces the Al-Zard racing car, integrating an advanced bio-computer system designed for direct neural interface with the driver to optimize performance. This technology becomes central to a major incident during the 15th Cyber Formula World Grand Prix, triggering significant controversy and consequences for the team.

Following the Al-Zard incident, Team AOI serves a one-year competition suspension. Nagumo later resurfaces in SIN, approaching Jotaro Kaga as the team struggles with inferior equipment upon its return. He provides Kaga with a prototype vehicle, the OGRE (AN-21), developed from the same technological foundation as the Al-Zard series. Sharing design lineage with the Asurada, the OGRE stands as a capable rival despite its experimental nature. It presents considerable control challenges, demanding exceptional driver skill and deep trust between machine and operator for optimal function. Nagumo's strategic provision of this prototype facilitates Kaga's intense rivalry with series protagonist Hayato Kazami during the 17th Cyber Formula World Grand Prix.

Visually, Nagumo possesses distinctive shoulder-length purple hair and black eyes, aligning with an adult demographic within the series. His operational methods involve utilizing technological superiority and exploiting team dynamics. His actions consistently demonstrate a focus on achieving competitive dominance through advanced engineering, often bypassing conventional sporting ethics. This approach positions him as a catalyst for conflict, particularly through his introduction of bio-computer systems that challenge the traditional driver-machine relationship in Cyber Formula.