Louise Françoise de la Baume le Blanc de la Vallière, third daughter of the noble family La Vallière who owns the north-eastern territory of Tristain, is the main female character. She is a second year student at the Tristain Academy of Magic. Louise is a terrible mage who is often scorned by her fellow classmates because every spell she casts fails, so she is nicknamed "Louise the Zero" after her zero success rate and zero attributes. This has led her to be very bitter and occasionally cruel in the way she treats her future familiar Saito.
At first, she treats Saito like a dog, making him lie on a straw bed, and even getting naked in front of him. She used to make him dress her and still makes him wash all of her clothes (including her underwear). As is typical of Rie Kugimiya's voice roles as tsundere type characters, Louise at first hates Saito, but because of various situations, grows fond of him and even harbors feelings of love for him.
From the start of the second season Louise changed the way she treats Saito. When she thinks he has perverted thoughts about other girls, or is jealous of or mad at him, she quickly beats him with a whip or blows him up with her magic, later into the third season getting into the habit of kicking him in the groin from behind on multiple occasions. In one instance within the second season Louise whipped Saito for hours until he had wounds all over his body (Though all had disappeared by the next scene) and later on buys a more brutal type of whip. All this is portrayed in a comical manner as is seen much more as the story progresses.
Later it is revealed that Louise's failure in performing magic of any of the four basic attributes is because, in fact, her magical affinity is with the rare and powerful Void element, hence being known as the Void Wizard since then. This relies, at first, on the cooperation of Saito's ability to trigger it, even though they do not get along.
