The Familiar of Zero

Louise is a student at Tristein Magical Academy. She is known to be quite a screw up when it comes to her magic. One day, a ceremony takes place where each student is to call forth a being or entity that will become his or her familiar. For Louise, her familiar comes in the form of a boy named Hiraga Saito. Somehow, he managed to get transported from his world into hers, and shortly after became her familiar.