At Tristain Academy, magic student Louise is mocked as "Zero" for her inability to cast a single working spell, until her familiar-summoning ritual pulls Saito Hiraga, an ordinary Japanese teenager, into her world instead of a proper familiar. Bound to Louise by magical law, Saito adjusts to serving a hot-tempered noble while uncovering unexpected fighting instincts of his own. This manga adapts the early volumes of the original light novels, following Louise and Saito through academy life and their first clashes with rival students like Kirche.