Princess Lupica of a distant world has loved Rio, the local tofu seller she grew up alongside, since they were children, and is convinced he does not feel the same. Her answer is the galaxy's most powerful love potion, sealed in a temple that supposedly opens only for the universe's most lecherous man. When her computer names Ataru Moroboshi, Lupica sweet-talks him into helping and then abducts him outright, sending Lum, with her friends Oyuki and Benten, off on a chase across the galaxy.