The Legend of Ubirajara.

In order to earn a warrior name, the son of Araguaia chief wanders the forest, falls in love with a girl from the Tocantins tribe, and defeats their bravest warrior. When his true identity is discovered, he makes a deal: promises to fight the Tapuias, another tribe which threatens the Tocantins, marries the Indian girl, and establishes the Ubirajara nation.