Even during the height of World War II, the small island north of Hokkaido where brothers Junpei and Kanta Senou live remains practically untouched. They spend their days gathering eggs and imagining themselves as Giovanni and Campanella, the heroes of Night on the Galactic Railroad, their favorite novel.

But soon the war ends, and Soviet troops come to occupy the island. As their situation becomes increasingly unstable, the two brothers manage to form an unlikely bond with Tanya, the daughter of a Soviet officer. Even so, it may be too late for their lives to be as carefree as they once were.