While trying to save a bear cub from drowning, Yakari falls into the river and hits his head on a rock. By the time he washes ashore and is found by a distraught bear mother, he has forgotten who he is. The she-bear is convinced that he is her son, turned into a human by the Bear Spirit and begins to train him for his new life. Can Yakari's friends find him before he disappears into his new world for good?