She is the third daughter of the Vallière family, an aristocratic family well known in Tristain. She attends the Tristain Academy of Magic as a second, and later third year student. She is known as Louise the Zero due to her spell casting success rate of zero and apparent lack of any elemental affinities. Louise is a petite girl with long wavy pink hair and pink eyes. She is usually seen in her school uniform, which consists of a white blouse, a gray pleated skirt, and a long black cloak. She wears the school's emblem tied to the collar of her shirt, along with long, black socks that go up to her thighs and a pair of black mary jane shoes. Her outfit lacks significant deviation from the Academy standard uniform. Her nightwear typically includes a large sheer nightgown. Throughout the light novels and show, she is seen wearing other clothing. When Saito and Louise are sent to Tristania to gather intel, Louise is shown wearing a simple sleeveless black dress, with a black beret, pink kitten heels with fabric straps, and an ornamental necklace. This specific outfit may be her casual outfit, but it only appears in this one instance. When she and Saito are recruited by Scarron to the Charming Fairies Inn, she wears the inn's uniform; A short open back camisole with high mary janes, a white thigh strap, and a large fabric choker with a bow. While Louise strives to act like a proper noble – collected, proud, and powerful – her mercurial nature often leads to impatience, temperamental outbursts, shyness, and recklessness. Conversely, she is capable of great generosity, selflessness, thoughtfulness, and active support. Her magic failures and subsequent disapproval from family and peers have left her with a strong need to prove herself and gain affection and recognition, traits that have led her to risk herself during the Invasion of Albion, the Gallian Royalty War, the rescue of Tabitha, and the fight against the Ancient Dragon. Louise is the third daughter of the Duke de La Vallière and Karin, Duchess of La Vallière. She later becomes a lady-in-waiting for Henrietta, Queen of Tristain. After Louise's void was revealed to her family, Henrietta made Louise her heir, thus the Crown Princess of Tristain.