Louise Valliere is a second-year student at the esteemed Magic Academy High School, but all of her classmates call her 'Zero Louise'. While no one doubts her magic ability, it is just that all of the spells that she casts go wrong, usually with disastrous and explosive results. Rumour has it that none of the spells that she tried to cast have ever gone as expected, which is how she picked up her nickname — Zero.
One of the most important second-year student rituals is the summoning of a familiar. A familiar once summoned will stay with the magician for rest of their life. A mage's magical familiar can appear in the form of any creature — as small as a mouse, as a fearsome fire salamander, and perhaps even as a dragon for an exceptional mage. True to form, Louise's familiar summoning spell goes very wrong and pulls Hiraga Saito from his life as a high school student in Japan into the magic world. The ritual is sacred and once started, cannot be changed, so Louise accepts her fate and gives Saito a kiss (on the lips) to seal their bond. The other students take delight in teasing Zero Louise at having summoned an ordinary commoner as a familiar, but they have forgotten that familiars are magical creatures and by their nature — are never ordinary or common.