Three high school girls get transported to a fantasy world, bestowed with magical powers. They team up to save the world from destruction by rescuing a kidnapped princess whose prayers keep it alive.

Three high school girls named Hikaru, Umi, and Fuu. On a class field trip to Tokyo Tower, they are magically transported into the fantasy world of Cephiro. They are immediately greeted by the mage Clef, who tells them that the world is dying after the priest Zagato kidnapped Princess Emeraude, whose prayers maintain the state of the world. Without her singing, Cephiro is on the brink of collapse. Imbued with magical powers as the Magic Knights, Hikaru, Umi, and Fuu must learn how to work together to survive and save Cephiro.