Giovanni lost his sight in a childhood accident and has lived in isolation since his father Pierre disappeared. He supports himself by producing Braille books while attending school, where classmates ridicule him. His closest childhood friend, Campanella, has also vanished from his life.

On the day of the Galaxy Festival, Campanella unexpectedly returns and invites Giovanni to join him. While searching for his friend among the crowds, Giovanni is pushed aside and mocked. When he finally reaches Campanella, a flash fills the sky and Giovanni loses consciousness.

He awakens aboard the Galactic Railroad 999, a train traveling through the Milky Way toward the Southern Cross. Along the journey, he repeatedly encounters figures resembling Campanella, each with a different name and role. Their stories of the constellations—including Phaethon and the Swan, and Orpheus and the Lyre—feel strangely familiar. Giovanni gradually realizes that they are stories his father once told him.

Near the Southern Cross, Campanella asks to exchange coats with him. Giovanni’s sea-otter coat was made by Pierre, once a hunter. A mysterious voice then declares that Pierre is not the noble ruler Giovanni imagines but a fugitive. Disturbed by the contradiction, Giovanni leaves the train and continues alone to the Island of Loss.

There he finds Pierre and admits that he has imprisoned his father within the island because he could not accept the truth. Seven years earlier, Pierre drowned while saving Giovanni from the accident that took his sight. The many forms of Campanella merge with Giovanni’s memories of his father, allowing him finally to acknowledge Pierre’s death and release him.

Giovanni awakens in the real world. He remains blind and must return to the same work and school, but he no longer carries his father as a disappearance shaped by denial and guilt. Remembering Pierre with love, he begins moving forward without feeling entirely alone.