Ronya 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.
Ronja is the only daughter of Mattis, a bandit leader who lives in a castle in the middle of a large forest. When Ronja grows old enough, she ventures into the forest to interact the strange and magical creatures that live there. She learns to live in the forest through her own strength, with the occasional rescue from her parents. Ronja's life begins to change, however, when she happens upon a boy her own age named Birk.