The Familiar of Zero

Meet Louise, a budding magician. The students at the Tristein Academy call her "Zero Louise", due to her current record of zero successes with magic. In fact, her magic tends to go spectacularly wrong. Now, as an important test of her aptitude for magic, she must summon a familiar to be her servant. At this critical moment, she summons up all her magic and wishes for a familiar that is "devoted, beautiful and powerful", and gets... Hiraga Saito, an ordinary Japanese boy. It's difficult to say who is more surprised and dismayed, but the rules don't allow for second attempts. Louise is stuck with her strange familiar, and he with her.

Synopsis from Anime News Network