In Too Deep by Erin Trejo

Bellmont has been in his family for generations, each son following the traditions of those before him until Ares. Trained from a young age in a world of darkness and blood, ruthlessness is a way of life.
When Ares spots Sage, he is confused by her pull on him, as women have no value in their world. Watching her from afar quickly becomes unsatisfying, and the decision to kidnap and keep her for himself is made.
Ares begins to question his father and the secrets he keeps, learning why there are so few women at Bellmont. The secrets his father kept stun Ares and his father’s expectation to accept the new order.
When Ares discovers Sage is missing, he vows to find those responsible and destroy them. With help from an unexpected ally, Ares unleashes his inner demon destroying all in his way.
Can the darkness in Ares survive in Sage’s light?