The Alien’s Torment by Luna Kingsley

Alien warrior Ondin is intelligent, cocky and flirtatious—and put in charge of the rescue when the female who wants nothing to do with him falls into enemy hands.

When Willa was accepted into the intergalactic educational medics program, her life changed for the better. Always the shy wallflower, she never had high hopes of escaping her old life for something better. Her plan to stay out of trouble and focus on her schooling doesn’t last long, however, when she’s captured again by the aliens looking to use her as a science experiment.
Being confident isn’t a bad thing, at least, that’s what Ondin believes. He thinks in ways his alien brothers don’t. Always steps ahead of his enemy. When a job needs to be done, he’s the one to make sure it’s handled. So when Willa is recaptured, he takes the blame and offers to go after her. He’s unprepared for what he finds and for how it will permanently change him.
Together Willa and Ondin are forced to rely on each other to make it back over the mountain, carrying a secret with the power to disrupt life on the sky island forever.