In a hilarious solar system adventure, the Nohara family gets entangled in a dispute over Shinnosuke's little sister, Himawari. When Himawari steals Shinnosuke's crème caramel, a rift forms between them, leading to unexpected consequences. Mysterious figures intervene, whisking the family away to Planet Himawari by UFO. There, they discover that Himawari must become the planet's princess to avert a looming catastrophe for Earth and Planet Himawari, as decreed by the enigmatic Sunday Goronesky the Great.