Yukiguni no Oujisama
English name: The Snow Country Prince
Genres: Slice of Life
Type: Movie, Episodes: 1
Aired: Dec 21, 1985
Studio: Toei Animation
Source: Book
Rating: G - All Ages
Synopsis:
Koichi and his sister Yuki befriend Hanaguro, a swan who has flown to Japan from Siberia. Hanaguro is attacked by a dog, and the cowardly Koichi flees, but that night he has a dream in which he is whisked away to the Kingdom of Snow Prince, where he finds the bravery to help the other swans.

(Source: The Anime Encyclopedia)