Denka is an extraterrestrial prince from the planet Ume, which was destroyed in a catastrophic explosion. He and his royal family escaped their doomed world in a spacecraft shaped like a traditional Japanese clay pot used for storing umeboshi. This vessel, surprisingly spacious inside, became their home on Earth.

As prince of the displaced royal household, Denka belongs to a family including his carefree King father, his graceful Queen mother, and retainers like the passionate chamberlain Benishoga and the troublesome robot Gonsuke. Their customs and values often clash humorously with Earth norms as they adapt to terrestrial life; the King, for instance, adopts the appearance of a middle-aged Japanese man wearing wooden sandals.

After Earth boy Taro Nakamura discovers their spacecraft, Denka forms a close friendship with him. Denka frequently uses advanced extraterrestrial technology from the ship to help Taro overcome daily challenges and dilemmas. This dynamic of solving problems with futuristic tools shares conceptual similarities with later Fujiko F. Fujio works.

Denka's personality contributes to the comedic and chaotic scenarios experienced by his family. While specific character evolution across the manga serialization (1968-1970) or the original 1969 anime adaptation is not detailed, he consistently functions as a central figure driving the narrative through his interactions with Earth and his family. A 1994 theatrical short film attempted a reintroduction, though no substantive information about altered traits within that production is available.

Denka's full name incorporates a deliberate pun connecting his home planet ("Umeboshi") with his princely title ("Denka"). This wordplay extends to their clay pot spaceship and their identity as refugees maintaining their alien heritage while adapting to Earth.