The Familiar of Zero is the first volume of The Familiar of Zero.
"Who are you?"
Hiraga Saito awoke to find a pretty girl asking him that question. Looking around, he found himself in an unfamiliar place, people dressed as magicians surrounding him and the girl.
The girl, calling herself Louise, explained that she had "summoned" him from his world to be her "familiar". Saito's confusion grew, especially after she kissed him and claimed it was a "contract"! My first kiss, he lamented, but before he had even a chance to become angry, strange symbols etched themselves into his left hand, marking him as a familiar!
While searching for a way to return home, Saito must cope with being forced to live with Louise, as her familiar...
And so begins Hiraga Saito's comedic life as 'Zero's Familiar.'
Note: Above is the cliff notes of the book seller. Some times not very good english.