Fantastic Adventure Of Yohko: Leda

Yoko Asagiri is in love, but is afraid to confess her feelings so she writes a song to express her feelings. Much to her dismay, the love song she wrote acted as a bridge connecting the world in which she lived in to that of Earth's alternate world called "Ashanti." There, the ruler of that world wants her song so that he could use it to open a doorway to Yoko's world and conquer it with his armies. Using the artifacts left behind by the legendary warrior Leda who prophesized her arrival, Yoko and her newfound friends must stop the tyrant's ambition and return both worlds to their proper place and balance.

Synopsis from Anime News Network