The Familiar of Zero.

Louise Françoise Le Blanc de La Vallière’s name is so long and her spell-casting skills are so poor that everyone at the Tristain Academy of Magic just calls her “Louise the Zero.” Louise’s humiliation only increases during an important second-year test, she inexplicably summons Saito Hiraga, a totally normal teenager from Tokyo. Now she’s stuck with him and Saito’s stuck with the lousy life of being a familiar.