In 1943, during the Pacific War, 12-year-old Mahito Maki's mother Hisako is killed in a hospital fire in Tokyo. Mahito's father Shoichi, an air munitions factory owner, remarries his late wife's younger sister, Natsuko. They evacuate to her estate in the countryside where they live with several old maids. Mahito struggles in the new town as he continues to grapple with grief, is pestered by a mysterious grey heron at the estate and is cold and distant towards Natsuko, who is now pregnant. Pursuing the heron, he discovers a ruined and sealed tower in the woods near the house and makes himself a bow and an arrow from the heron's feathers.