Demon Healer - The Goddessverse Fantasy Series, #3

Kai's competency as a warrior masks a broken heart. Wanting to distance himself from reminders of what he cannot have, the Reformed Realm demon takes a job in Tartarus, the Underworld's famed prison. Arke spent untold centuries in Tartarus' hidden catacombs. All the recently freed messenger goddess wants is her wings - and to put as much distance as possible between her and her sister, Iris, goddess of rainbows. Now Kai is tasked with getting Arke to safety.
He knows he can do this-he's an elite guard with an impressive wingspan. Except the sensations coursing through his wings' sensitive membranes tell him Arke might be more than just a high-risk client. She might be his future.