Little Prince and the Eight Headed Dragon

Prince Susano's mother dies; when his father tells him she has gone to another place, he sets off in search of her. He builds a boat and goes to see, first, his brother, in his crystal palace in the land of night (where he causes much damage to the palace, but his brother still gives him a magic ice crystal). Next, he fights the fire god, who gives him a magic bird after Susano defeats him, with help from the magic crystal and his little rabbit sidekick. Susano also picks up another traveling companion, a large but dim villager. Next, he goes to his sister, in the land of light. As with his brother, though, he causes much unintentional damage; his sister, who also happens to be the sun, goes off to hide in a cave. The frantic villagers stage a party (in the original legend, an orgy) outside the cave and trick her into coming outside again. Finally, Susano finds a little princess whose land is being threatened by an 8-headed dragon. With the help of a flying horse (who we later learn was sent by his sister) and his sidekicks, they get the dragon a bit drunk and take out one head at a time (mostly, though two of the last three take each other out). Little Prince and the Eight Headed Dragon featuring Tomohito Sumida and Chiharu Kuri is free on Tubi. It's an action & adventure and animation movie with a better than average IMDb audience rating of 7.1 (267 votes).