It is the first work in what is regarded as Osamu Tezuka's early science fiction trilogy, consisting of Lost World (1948), Metropolis (1949) and Nextworld (1951).

Scientists know nothing about the planet and decide to venture to it in order to discover its inhabitants and conditions.

The planet, named Mamango, broke off from Earth 5 million years ago and has come back for the first time since.

The team soon discovers that criminals have stowed away on their space ship and that they have come to Mamango for their own devious reasons.

When the English adaptation was published in the United States on July 30, 2003, both books were combined into a single volume.