Crimson Warrior by Samantha Whiskey

There’s one bed and she’s my best friend…
For over two centuries, I’ve been the king’s assassin—his master of combat.
It’s my job to strategize and to train potential warriors, but I’ve never looked at any of them the way I look at Olivia—my best friend.
She’s all subtle curves, rich chocolate eyes, and as deadly as she is sexy.
With a new war knocking at our borders, the king orders us to awaken the Hunters—six of the world’s most lethal vampires.
Olivia’s family has guarded them for almost as long as she’s kept her secret from her parents:
She’s not some docile, mated lady-in-waiting, she’s actually a royal bodyguard.
But to convince her archaic family to wake the Hunters, Olivia has to come home with her mate.
No problem. How hard can it be to fake it for a couple of weeks?
But the line between pretending and reality quickly gets blurred.
The longer we play the part, the more I realize that Olivia and I are a perfect match.
Now I’m not only battling a nefarious plot against us, but my own primal urges to claim Olivia.
I might be the most lethal vampire on the planet, but she’s the only one who can bring me to my knees.
And when I’m forced to choose between my heart and my duty, everything we’ve worked for could come crashing down.