Tatsuo Seno lives on Shikotan Island with his two sons, Junpei and Kanta, and his fisherman father, Genzō. Serving as head of the village's firefighting force, he becomes the sole parent to his sons after his wife's death. When severe food rationing grips the Japanese inhabitants following the Soviet occupation post-World War II, Tatsuo risks everything by secretly distributing vital food from the former Japanese military's emergency stores to the starving villagers, driven by duty and self-sacrifice.

His brother, Hideo, discovers the hidden food cache. Rather than support Tatsuo's mission to feed the community, Hideo attempts to smuggle the supplies for personal profit. This betrayal leads Soviet soldiers to capture Tatsuo directly at the cave storage site as he tries to secure food for the villagers.

During the forced deportation of Shikotan's Japanese population, Soviet forces separate Tatsuo from his family, detaining him in a different internment camp. His sons, alongside their teacher Sawako and Hideo, embark on a perilous journey to reach his camp. They achieve a brief reunion where Tatsuo makes a determined promise to find his family again despite the overwhelming odds. This moment marks his final direct interaction with his sons within the film's narrative.