Kiss of a Blade by Lea Griffith

Her heart is as cold as the blades carried against her skin.
Blade has known the heights of joy and the depths of pain, and walks the knife’s edge between them every day. Death is what she excels at; indeed, it gives her peace. But her world has focused to the very sharpest point, and it’s up to her to make sure First Team’s final step is flawless. She will not allow anything, or anyone, to stop her.

His world was shredded by loss and betrayal.
Ken Nodachi lost his sister and niece in a brutal hit that seared all the joy from his life. He has tracked the Collective since that day, and now has one of their finest in his sights. He believes that pain is about to be redeemed. But he’ll have to be quicker than the blade aimed at his heart because the vengeance he seeks could be what destroys him.

Joy and pain. Two sides of one coin. Retribution draws them together, but before all is said and done they will learn love can either break you or make you stronger.