The Ancient Magus' Bride

With her mother dead and father long gone, Chise Hatori has spent her childhood being passed unwanted from relative to relative,
until she finally makes her unfortunate way to a strange and improbable auction block.

Offered as a “Slay Vega” to the highest bidder, Chise is purchased by the (literally) boneheaded Elias Ainsworth,
who promises to take her on as his apprentice.

Elias is a mage, and his world is one of dragons and faeries - but before Chise can begin to get accustomed to all of this,
Elias drops another bombshell. Apparently Chise isn't just intended to be his apprentice - she will also be his bride.