Two pairs of young lovers find themselves entangled in a conflict between two rival kingdoms, Isa and Paro. Izu and his wife Marin are simple farmers living in the village of Saki, which lies directly between these kingdoms. Although their village is not as magnificent as Isa or as militaristic as Paro, it possesses a remarkable tree known as Windaria, to which the villagers offer prayers for good memories. When war breaks out, Izu decides to join Paros army and receives a motorbike as an incentive. Before he departs, they both make a vow: He will return to her, and she will wait for him until then. The other two lovers are Jill, the prince of Paro, and Ahanas, princess of Isa. Initially, they wish to stay clear of the rapidly intensifying conflict, but after Paros king dies at his son's hand in a dispute over the war, Jill is left with no choice but to fulfill his father's final wish: the conquest of Isa. The only issue is that he had promised Ahanas that he would not participate. Windaria is a parable about war set in a fantasy land filled with unicorns and ghost ships.
Although the story was originally conceived for the production of an anime, Windaria first appeared as a novel titled Douwa Meita Senshi Windaria four months prior to the movie's release. As stated in the postscript, the author believed this reading would further entice people to watch the film.The movie was broadcasted several times on Yomiuri TV's Anime Daisuki! program. An English version was made available under the title Once Upon a Time by Harmony Gold in 1987. However, in order to make it suitable for a younger audience, major changes were made: the exclusion of some nudity and violent scenes, modification of the script, new character names, and added narration.In Japan, Windaria was initially distributed to home video by Victor Entertainment, which later released it on DVD on December 16, 2000. In the US, it was made available on VHS as Windaria by Streamline Pictures on August 1, 1993, and on DVD as Once Upon a Time by ADV Films on March 16, 2004. Additionally, a video game adaptation titled Dungeon of Windaria was released in Japan by Nintendo on May 15, 2008.