In Muromachi Japan, an Emishi village is attacked by a hideous demon. The last Emishi prince, Ashitaka, kills it before it reaches the village, but it manages to grasp his arm and curse him before its death. The curse grants him superhuman strength, but it also causes him pain and will eventually kill him. The villagers discover that the demon was a boar god, corrupted by an iron ball lodged in his body. The village's wise woman tells Ashitaka that he may find a cure in the western lands that the demon came from, and that he cannot return to his homeland.