Magic Knight Rayearth started as a manga, consisting of 6 books then grew to an anime. It starts out with three girls from Tokyo, going to Tokyo tower on a School field trip and being whisked away into another world.
They land in the a different world called Cephiro, where magic is used and the world is supported by the pears of one person, called the pillar.
Soon all three girls, Hikaru, Umi, and Fuu, are thrown into an adventure, getting weapons and fighting magical enemies. In the process Magic Knights end up killing the pillar at her own request and so the three girls are sent back to Earth with heavy hearts. The girls stay in there world for a while but soon decide to return to Cephiro with a new problem at hand. Now they have to fight for a new pillar and the world of Cephiro itself.
The world has been attacked by three other worlds, with people that will stop at nothing to become the next pillar. The three girls have to fight with everything they have, but in the end It is Hikaru who becomes the new pillar.