onya lives happily in her father's castle until she comes across a new playmate, Birk, in the nearby dark forest. The two explore the wilderness, braving dangerous Witchbirds and Rump-Gnomes. But when their families find out Birk and Ronja have been playing together, they forbid them to see each other again. Indeed, their fathers are competing robber chieftains and bitter enemies. Now the two spunky children must try to tear down the barriers that have kept their families apart for so long.

Overview from themoviedb.org