A normal high school student, Hiraga Saito, is transported into another world. The witch who summoned him is Louise. Although very cute, she is also very haughty and has no talent for magic. In fact, she is popularly known as "Louise the Zero" after the success rate of her magic. Before Saito could gain his bearings, Louise suddenly pushes her lips to his. Mysterious letters appear on the back of his hand and he becomes her familiar spirit.

So Saito begins to live with Louise in the boarding house of Tristein Magical Academy. Every day, he is abused, scolded, (and loved?) by this haughty but cute girl. This is how his exciting days filled with courage, humiliation, and love begin.