The Darkest Pleasure 1 (Lords of the Underworld #3.1)

Even if I'm afraid of him and hate him, I can't forget him… Exiled from Olympus, Reyes, a Guardian of the Gods, lives in a forest in Budapest for thousands of years with a demon sealed away in his body. A tourist from the United States, Danika, meets him and her life completely changes. Not knowing the reason, she becomes imprisoned in a castle of terrifying warriors. Though she was lucky enough to escape, her life became one of wandering around in hiding. Even so, she caught herself unable to forget the Guardian Reyes who toyed with her feelings. He's not human. He's a man too dangerous to love, but...