6 months after the earthquake disaster in Sendai City, Nakagaki Kazumasa is a young man who has lost his job. He encounters a dog named Tamon on its dog tag, who lost its owner in the earthquake disaster. Kazumasa decides to take Tamon in, and the dog becomes attached to him and his family, but Tamon always seems concerned about something in the south direction. One day, while Kazumasa is involved in a dangerous incident, Tamon disappears. Later, in Shiga, Tamon is with Sugai Miwa, who has a sad secret. Kazumasa reunites with Tamon, and they start a new life together. Nevertheless, Tamon heads south because Tamon has a promise it wants to keep to a boy.

One day, taxi driver Koji Usami is tasked with driving 85-year-old Sumire Takano from Shibamata, Tokyo to a senior care facility in Hayama, Kanagawa. Sumire asks Koji to make some detours. Gradually opening up to her, Sumire begins to tell the story of her grand past...