Umimaru Kidō is an assistant professor of psychology at Genjōsai University who also possesses considerable expertise in computer technology. He harbors intense romantic feelings for Rem Ayanokōji, often rivaling Enkō for her attention.

During *Dream Hunter Rem III: Hidden Dream - Legend of the Headless Warrior*, Kidō partners with Tatsuhiko in Tokyo. They analyze a stolen "dreaming doll" using specialized machinery designed to measure its supernatural energy outputs. While Tatsuhiko pursues a rumored Taira clan treasure, Kidō concentrates on documenting the doll's paranormal properties. His involvement ends tragically when a spectral horseman destroys their laboratory; Kidō and Tatsuhiko become trapped inside the ensuing inferno.

No additional narrative developments, background origins, or further appearances in other media are documented within the provided sources.