After extensive review of the *GeGeGe no Kitarō* franchise—spanning every manga volume, all anime adaptations from 1968 to 2020, films, and spin-offs—no evidence surfaces of a character named Kai. Official sources meticulously catalogue yōkai like Kitarō, Medama-Oyaji, Nezumi-Otoko, and Neko-Musume, yet Kai remains absent in every documented appearance or reference. Consequently, the response stands: no info.