During a night in the midst of the Pacific War, Makoto Maeda loses his mother, causing him to become withdrawn and silent. The following year, his father, Katsuichi, who runs a military supply factory, remarries his late wife's sister, Natsuko. Makoto and his father move to live with his mother's family. One day, Natsuko goes missing in the forest, causing a commotion at the estate. Makoto, along with an old servant named Kiriko, enters the back door of a tower to search for Natsuko but ends up being trapped inside. Inside the tower, after encountering a talking heron, a fantastical adventure begins...