I love the series as a whole and was interested in this prequel film. It isn't very good; there is just too much plot for this story to fit into 75 minutes. The manga version has more character development and explains where the mediator came from, why the main antagonists are after Emelia, the origins of Puck...and these are all missing from this film.
Read the manga version of this for a better prequel explanation as this film falls flat. It is far too confusing.