Hiroto grows up in Japan with his mother and father. For as long as he can remember, an asteroid, visible in the sky, has slowly been approaching Earth. The predicted collision would be fatal for humanity. The Japanese government announces the construction of robust spaceships that would take the entire country’s population to deep space, and as a child, Hiroto travels with his family toward the launch destination. Before they arrive, it is revealed that the ships which were built were not strong enough to carry anyone to space.  Without this hope of escape, most people return to their normal lives. Hiroto enjoys this time with his parents with little anxiety. One day, Hiroto’s mother tells him they are going Christmas shopping, but she brings him to an American office, where he meets Dr. Hamilton, a colleague of Hiroto’s parents when they lived in America. Dr. Hamilton designed the only spaceship that was able to launch before Americans entered a destructive war which prevented them from building any more. Knowing this would be their son’s only chance of survival, Hiroto’s parents leave him with Dr. Hamilton. Hiroto does not see his parents again. He grows up on the spaceship and has a job monitoring the solar sail. As the only Japanese person onboard the ship, he participates in the cultural-enrichment program at their school, teaching kids to play Go. Kids complain that unlike in chess, there are no heroes in Go. Sometimes he teaches his girlfriend, a singer and originally a Spanish speaker, some words from his language, and he describes moments from his last days in Japan to her. He describes the Japanese as community-oriented and calm in the days before the apocalypse, but she misunderstands them as being resigned. One day at his job, Hiroto notices a tiny error in the motion of the sail. In a meeting with the ship’s experts, he learns that there is a gash in the sail, which will keep growing if not fixed, and may eventually destroy the ship’s ability to move at all. Hiroto volunteers to fix the sail, as he is familiar with its structure because of his job. He walks out on the sail with the bare minimum supplies he needs to survive, however he bumps a fuel tank against the ship, which damages it. He must then choose between using his return trip fuel to fix the sail, or returning to the ship and allowing the gash to continue growing. Hiroto chooses to fix the sail, and is unable to return to the ship as a result. He drifts off into space, thinking of a walk he once took on Earth with his father.