In January 1841, Manjiro, a poor, 14-year-old fisherman, is sailing off the coast of Shikoku, Japan. He and his four companions, Denzo, Jusuke, Goemon, and Toraemon, have yet to succeed after three fishing days. Manjiro questions what lies across the sea, what the dark streaks in the water are, and why the wind is so strong, to the annoyance of his friends. His questions lead to answers: barbarians lie across the sea, mackerel are in the water, and a dangerous storm is rolling in.

An ocean current catches the boat and strands the fishermen at sea for days. They use up their food and water and prepare to die. Manjiro confesses that his greatest wish is to become a samurai. The others laugh at him. He spots an island covered in albatrosses. At first, the fishermen are hopeful, but they soon realize the island is barren except for the birds.

The fishermen scrape by on the desolate island by hunting birds and raiding their nests. Manjiro attempts to be creative with how they prepare birds to make their meals more enjoyable. Eventually, the birds leave, making food harder to come by; the boys survive on rainwater.

Manjiro and Goemon discuss becoming samurai, and Manjiro clarifies that he wants to be a good, honorable samurai, not a cruel one.