Kei Tsukikage is the energetic younger brother of Toshi Tsukikage, sharing his sibling's passion for the fictional series Ganbaman. He typically rides a tricycle that flies when equipped with an umbrella. Functioning primarily in a supporting narrative role, Kei regularly accompanies the main trio but avoids direct combat against antagonists. His character exhibits the playful nature and high energy typical of young children. Kei is identified as a direct descendant of the historical Shinsengumi member Yamanami Keisuke, reflecting the series' theme of ancestral legacy. Information regarding his full background story, development in additional media like movies, OVAs, or spin-offs, and significant narrative arcs beyond his established supportive and comedic role is not provided.