Tsukikage Kei, the younger brother of Toshi Tsukikage, is a fifth-grade descendant of the Shinsengumi through his ancestor Juurou Tsukikage. This energetic and curious kindergarten-aged child occasionally aids the main trio in their missions against the Kurotengu organization when they encounter significant obstacles. Kei is an enthusiastic fan of the fictional superhero series "Ganbaman," particularly idolizing the team leader, Gamba White. His signature mode of transportation is a distinctive tricycle capable of flight when equipped with an umbrella, providing limited airborne mobility. His modern name derives from Yamanami Keisuke of the original Shinsengumi. Though the age gap with the older protagonists often excludes him from their activities, Kei remains determined to contribute whenever possible.