Guarding Brynn

He has one job. Keep her safe.
After leaving the military, Jace isn't looking for another job that can get him killed. Problem is, he helped a man in trouble and as a result found himself in the middle of a pharmaceutical war.
He should walk away.
Once he meets the man's daughter, however, his heart tells him to stay and when she becomes a pawn in that war he's hired to protect her. The job should be just what he wants - a way to get close to her -- except he knows how the protection business works. No fraternization with the client.
But for this particular job, fraternization is not only allowed, it's strongly encouraged.
He doesn't know how to react to the unusual clause.
Should he remain cool and distant in spite of that caveat because he's a nice guy and she's emotionally vulnerable? Or should he let his heart dictate his actions?