Umimaru Kidō holds the position of assistant professor in psychology at Genjōsai University, complementing this role with expertise in computer technology. His professional background facilitates involvement in supernatural investigations, primarily leveraging academic resources for analyzing psychological phenomena, particularly those related to dream entities.

He harbors strong romantic feelings for Rem Ayanokōji, the series' protagonist, establishing a recurring rivalry with another character, Enkō, who shares similar affections. This dynamic drives competitive interactions between the two characters.

His portrayal remains consistent across all appearances, with documented spin-offs, novels, and extended media beyond the original OVAs showing no significant evolution or expansion of his background or characteristics.