In medieval Japan, a boy named Sasuke and his sister live in a forest along with several young animals of different species.

One day, one of the animals (a young deer) is grabbed by an eagle and thrown into a lake.

The beast leaves the lake, revealing its true form: a female demon named Yakusha.

Sasuke then decides to seek a magician master to learn to fight against Yakusha to save Japan and avenge the death of his pet.

Since the creators of the English version preferred to liken Sasuke to the public perception of samurai, who were viewed as heroic, as opposed to the ninja, who were viewed as "sinister spies and assassins," MGM's publicity incorrectly claimed that The Adventures of the Little Samurai was the Japanese title of the film.