Three years into the conflict, Mahito Maki loses his mother in a devastating blaze at the hospital. Soon after, his father weds Natsuko, Mahito"s late mother"s younger sister. The family relocates from Tokyo to the countryside where his mother"s ancestral house stands. In that setting, a peculiar gray heron repeatedly mocks Mahito, as if it has taken a particular interest in him.
Struggling to accept his grief and adjust to an alien environment, the boy is stunned when he learns that Natsuko is expecting. The nagging heron, which can speak, insists that Mahito"s mother still lives. It lures him toward a mysterious tower near the house, promising that he can rescue her from death, yet Mahito remains skeptical.
One day Natsuko vanishes; Mahito sees her step into the tower and feels compelled to follow. He descends into a realm below his own, where life and death intertwine. While searching for Natsuko in this strange world, Mahito must grasp the true meaning of living if he hopes to return safely.
