In the 2030s Earth has been overrun by the Blue, which are mutated insect-like creatures that kill and harvest humans for food. Most of the surviving human race has moved to Second Earth, a huge spaceship that orbits the planet. Yuji and Marlene must work together to reach Second Earth and fight against the Blue.

Pen-Pen, the hat-and-tie-wearing prince of Penguin Land, turns up unexpectedly on little Mika's doorstep. and invites himself and his zany friends to stay.

The main character of the story is Fang, who was born to a hunting dog and a circus-runaway European wolf. Although Fang was raised by a human family, he is a wild animal after all, and is destined to live amongst nature. The story reaches its climax when Fang returns from the circus and faces his foe, a giant brown bear which killed his family.

Tezuka Osamu crafts a love story in the time when humans are expanding into space at the end of the 21st century, employing an omnibus form similar to Bradbury's "Martian Chronicle." Leaving the earth after marriage, a woman is left behind in space when her husband suddenly dies of a cosmic disease. Her friends on the Earth head for space to save the woman who was once everyone's ideal lady. Tezuka Osamu emphasizes his concepts that "love can save the earth" and "only love can save humans."