Saito is an ordinary Japanese boy who is summoned into a different world to be the familiar of Louise, landing in the Tristain Academy of Magic. He has the ability to use any weapon at an extremely high level of skill.
At first, Saito had no idea where he was, and was thoroughly disoriented. His attitude is generally carefree yet he blows up easily when anyone he cares for is in danger, particularly Louise. Though he at first wishes to return home, he adapts to his strange new situation relatively quickly.
There are runes inscribed into Saito's hand as a result of his being bound to Louise. ,These runes glow when his Gandalfr powers activate. As a Gandalfr, a familiar who exists to protect a Void Wizard, Saito has the ability to use any weapon at an extremely high level of skill. He also becomes significantly stronger, faster and tougher. This physical augmentation fades more or less instantly when he stops using the power, which can result in him falling unconscious if he had been previously wounded. He is said to be the left hand of god.
His partner is the talking sword Derflinger. Saito protects Louise with a passion, a result of both his duty as a Gandalfr and his feelings for her. He eventually falls in love with Louise, despite the abusive way she treats him.
The Familiar of Zero: The Alluring Beach
A fan service OVA episode with no plot development to speak of, packaged with series 3 in Japan.