Demon of Convenience — Cynthia Sax

The warmest of hearts is encased in a block of ice.

Mina has to bond with a demon. In return for his permanent protection, she will offer him unlimited power. When she asks her best friend for help, Taurinus -- a deadly assassin -- arrives instead.

Mina is horrified by the last minute substitution, but she is running out of time and has no other choice. She resigns herself to a passionless bonding of convenience… until one kiss changes everything.