A young boy and a girl with a magic crystal must race against pirates and foreign agents in a search for a legendary floating castle.

Ashitaka, a prince of the disappearing Emishi people, is cursed by a demonized boar god and must journey to the west to find a cure. Along the way, he encounters San, a young human woman fighting to protect the forest, and Lady Eboshi, who is trying to destroy it. Ashitaka must find a way to bring balance to this conflict.