"Uchūjin Pipi" is a science fiction anime series centered around Pipi, a small, alien creature from a distant planet who crash-lands on Earth. Pipi possesses unique abilities, including telepathy and the power to manipulate objects with its mind. The story begins with Pipi being discovered by a young boy named Hiroshi, who lives in a quiet rural town. Hiroshi, initially frightened by the strange creature, soon befriends Pipi after realizing its gentle and curious nature. Together, they embark on adventures to help Pipi find a way to return to its home planet while keeping its existence a secret from the outside world.

As the series progresses, Pipi and Hiroshi encounter various challenges, including government agents and scientists who become suspicious of unusual phenomena in the area. These encounters often lead to tense situations where Pipi must use its abilities to protect itself and Hiroshi. Along the way, the duo forms bonds with other children in the town, who assist in their efforts to shield Pipi from discovery. The narrative explores themes of friendship, trust, and the importance of understanding those who are different.

The series also delves into Pipi's backstory, revealing its origins and the reasons for its journey to Earth. Flashbacks and telepathic communications provide insight into Pipi's home planet, its species, and the advanced technology they possess. These elements add depth to the story, highlighting the contrast between Pipi's advanced civilization and the simpler life on Earth. The dynamic between Pipi and Hiroshi evolves as they learn from each other, with Pipi gaining a deeper appreciation for human emotions and Hiroshi developing a broader perspective on the universe.

Throughout the series, the tone balances lighthearted moments of humor and camaraderie with more serious undertones of danger and ethical dilemmas. The interactions between Pipi and the human characters drive the narrative, emphasizing the importance of cooperation and empathy. The story concludes with a heartfelt resolution as Pipi finally finds a way to return home, leaving a lasting impact on Hiroshi and the other characters. The series leaves room for reflection on the connections between individuals, regardless of their origins or differences.