What great graphics. My computer did indeed have some slowness with playback on the intensive scenes. I would recommend that you incorporate a quality button of some sort, since simply lowering the quality to medium seems to fix most chugging problems for me. As for the animations, this is superb. Great mix of style, animation, colors, and story. The only complaint I have about all of this is that sometimes there is too much going on the screen at once. The characters are rather complex in their designs, which is an okay thing when there is not a lot on screen, but in the intense graphics and fight scenes, it gets difficult on following whats going on for the most part. I am not familiar with the story/folksong, so this was an interesting story, and very executed. I understood it completely, but I feel some scenes was a bad choice in camera angle.
Anyway, great job! This graphical animation is fun to watch, and the music makes it exciting and fast-paced.