"21 Emon: Uchū Ike! Hadashi no Princess" is a science fiction anime and manga series that blends adventure, comedy, and space exploration. The narrative centers on 21 Emon, a young boy who works at his family's struggling inn, the Tsuzureya, in a futuristic setting. The story takes a dramatic turn when a mysterious spaceship crashes near the inn, revealing a barefoot princess named Paffy from the planet Altair. Paffy is on the run from the tyrannical Emperor Zordar, who seeks to exploit her planet's resources.

21 Emon, along with his robotic companion Gonsuke and the alien creature Monga, becomes entangled in Paffy's plight. Together, they embark on a journey across the galaxy to help her reclaim her throne and protect Altair from Zordar's oppressive rule. The group faces numerous challenges, including space pirates, intergalactic battles, and moral dilemmas, as they navigate the complexities of loyalty, friendship, and justice.

The series explores themes of courage and resilience, with 21 Emon evolving from a carefree innkeeper to a determined hero. Paffy's character adds depth to the narrative, as her royal background contrasts with her vulnerability and determination to save her people. Gonsuke provides comic relief while also serving as a reliable ally, and Monga's unique abilities often prove crucial in their adventures. The dynamic between the characters drives the story forward, creating a balance of humor, action, and emotional moments.

The plot is structured around episodic adventures that contribute to the overarching mission of defeating Zordar and restoring peace to Altair. Each episode introduces new challenges and allies, expanding the universe and deepening the stakes. The series concludes with a climactic confrontation that tests the resolve and unity of the main characters, ultimately delivering a satisfying resolution to their journey.