The Legend of Sirius was created in the early 80's or late 70's by a studio called Sanrio [Long Live Kero-chan!! -Ed.], the company that would later become famous for the Hello Kitty products. But don't assume that this is juvenile. First, a story on the history of the project: The producers were fascinated by Disney's Fantasia and wanted to be a part of the tradition to make quality anime. They collaborated with an American studio and made Metamorphoses: Winds of Change, a sort of precursor to this film. It was in the same format as Fantasia, one that told the story through music and sound. Being successful, they decided to produce a full-length animated feature. They also chose a theme that Disney had always found difficult to animate: fire and water. Since these elements are always in motion, they are the most difficult to give life to in animation. Furthermore, they hand-drew all the cels and employed a full orchestra for the music. The result was, I think, a first-rate film: the music itself is beautiful. (Remember, this was before the age of Miyazaki.)
Sirius is both a classic tale of forbidden love and a myth about the star of the same name: the brightest star in the northern sky, in the constellation Canis Major. It's a fantasy about Fire and Water, and the beauty of the pure elements. It's along the lines of the early, original style of Disney, when animation was pure, natural fantasy. This was one of the few films where I could feel the passion and effort that went into making it. Add to that the wonderful score, and that makes it one of my favorite films - a pleasure and an honor to translate.
(Thanks to James and Chris De Vries for astronomy information.)