Ukon Tanaka operates within the Tsubame Group, an antagonistic faction active during an alternate Meiji era. This organization resists monster registration laws, aiming to return supernatural beings to their pre-legal oversight state. As second-in-command of a trio led by Miki Saotome, Ukon exhibits light green hair and matching eyes. He projects bold confidence, openly boasting about his charisma and swordsmanship skills. His primary weapon is a samurai katana, reflecting his background as a trained swordsman whose career ended after a decisive tournament defeat.

Ukon displays fierce loyalty to Miki Saotome, consistently addressing her as "princess" and declaring himself her "knight in shining armor"—a dynamic strictly professional, not romantic. In combat, he favors direct clashes against foes like the Mobile Shinsengumi. Occasionally, Ukon provides comedic relief, such as suffering nosebleeds during incidents involving partial nudity, like an octopus yokai tearing Miki's clothing.