A boy with a drawing book meets a mysterious girl in the streets of Tokyo. They become friends and enjoy each other's fantasies.

In the 26th century, humans discover a humanoid race living on the distant world GO/7498/2, a dark-skinned, golden-eyed people who seem to eke out a primitive, carefree existence. However, a scout team from Earth discovers that there is more to them than meets the eye--they live in symbiosis with vicious reptilian parasites, and the Terran scientists have upset the delicate natural balance.

Nuclear testing has resulted in the abrupt evolution of the Fumoon, a tiny but highly intelligent humanoid race on a small island, who are detected by Dr. Yamadano. Except for a few witnesses including the detective Shinsaku Ban, and the young men Rock and Kenichi and Kenichi’s sister Pichi (Pinoko), no one believes him. The Fumoon are kidnapping animals from around the world to bring with them as they use their space ships to evacuate the earth, because they know Earth is shortly to be destroyed by an enveloping cloud of black gas created by a stellar explosion. The Fumoon intend to abandon mankind, but one Fumoon, Rokoko, who becomes good friends with Kenichi, tries to help Dr. Yamadano and the others to develop a space ship to allow a few humans to escape, with the help of Dr. Ochanomizu and Dr. Frankenstein.

The story of the manga centers around Marimo Nogami, a usually quiet fourth-grade girl in elementary school. However, a certain incident leads to Marimo's personal strength blossoming.