After losing his mother during the war, young Mahito moves to his family's estate in the countryside. There, a series of mysterious events lead him to an ancient and secluded tower, home to a mischievous gray heron. When Mahito's new stepmother disappears, he follows the heron to the tower and enters a fantastical world shared by the living and the dead. Embarking on an epic journey with the heron as his guide, Mahito must uncover the secrets of this realm and the truth about himself.