Kei Tsukikage is Toshi Tsukikage's younger brother. Both brothers are avid, dedicated fans of the fictional tokusatsu series Virtual Sentai Ganbaman. Kei is often seen riding a unique tricycle; this vehicle exhibits unconventional capabilities, including flight when fitted with an umbrella. He frequently delivers comic relief through exaggerated reactions and a distinctly childlike demeanor.

Within the narrative, Kei is a descendant tied to the historical Shinsengumi lineage, specifically carrying the legacy of Yamanami Keisuke. This heritage connects him to the series' central conflict. However, Kei does not wield a spiritual weapon or participate directly in combat alongside the main trio of descendants. His involvement stems primarily from his relationship with his brother and his occasional presence during group activities.