Heart of a Fighter by Grace Brennan

Cammie Samuels has been in hiding her whole life, not allowing herself to get close to anyone other than her fighter brothers. Her inner animal is rare, and the threat of discovery is all too real. It’s a hard way to live, but she’s made peace with her life, channeling her frustration into fight training, until a mysterious human shows up, shattering her illusion of peace.

After a terrible accident, Alex Kincaid has no memory of who he is or why he was looking for the Rocky River fighters. But when he meets Cammie, he’s certain she’s the one he’s been searching for. As pieces of his memory return, he’s left with more questions than answers, and though he’s falling for her hard, he knows he isn’t truly free to be with her until he figures out who and what he really is.

With danger approaching, Alex must recover his memory to save the woman he loves, or risk leaving her to fend for herself against an enemy who’s been hunting her for years.