[1][2][3] Strictly speaking, it is in the form of a picture story (emonogatari) with narrative captions attached to the illustrations.
Dankichi, an adventurous Japanese boy, and his mouse companion Karikō, wash ashore in a South Pacific island after falling asleep in a fishing expedition in the ocean.
They find the island is inhabited by natives; Dankichi becomes their king after defeating their leader, bringing "civilized" infrastructures (schools, hospitals, etc.)
and customs to the island and defending it from Western invaders.
In the post-World War II period, the manga was criticized for glorifying aggressionism and promoting racial prejudice; the island people were depicted as dark-skinned, thick-lipped naive barbarians in contrast to the "civilized" Japanese; they weren't given names, but numbers (number 1, 2, 3) by Dankichi.