Kyotaro Yamada is an FBI agent operating under the alias Kyotaro Imura. He works undercover as assistant to Menoa Bellucci, a Digimon researcher, to investigate her true activities starting in New York. When Eosmon emerges in Japan, linked to coma incidents affecting Chosen Children worldwide, Kyotaro accompanies Menoa there.
Physically tall with fair skin, he has black hair shaved below the crown and black eyes. His professional attire includes a grey shirt, dark grey necktie, black suit, and black shoes. His imposing height and blunt, direct speech create an intimidating presence, though he self-identifies as introverted. His mission is gathering evidence against Menoa and personally ensuring her arrest for orchestrating the coma incidents.
In Japan, Kyotaro collaborates with Chosen Children including Tai Kamiya (Yagami Taichi) and Matt Ishida (Ishida Yamato) against Eosmon. He provides tactical support in their initial cyberspace confrontation, equipping Kabuterimon and Angemon with containment tech. His abrupt departure after Omegamon destabilizes arouses Yamato's suspicion. Yamato tails him, witnessing a firearm exchange with an associate in a parked car and later discovering Kyotaro's hidden workspace filled with surveillance materials on Menoa and the Chosen Children.
Kyotaro confronts Yamato in a garage after Takeru Takaishi (Takaishi Takeru) and Kari Kamiya (Yagami Hikari) fall comatose. He reveals his FBI identity, explaining Menoa orchestrated the kidnappings to steal Koushiro Izumi (Izumi Koushirou)'s global Chosen Children list. Recognizing Menoa's plan to trap more victims using Eosmon clones, Kyotaro assists Tai and Matt in entering the Digital World for the final confrontation. Following Menoa's defeat and Eosmon's destruction, he arrests her, concluding his mission. His actions facilitate the crisis resolution.
His name "Yamada Kyotaro" (山田京太郎) uses the surname Yamada (mountain rice field) and given name Kyotaro (capital + suffix tarō). His alias "Imura Kyotaro" (井村京太郎) uses the surname Imura (well village).