Speak in Fever by Atlas Jones

Newt has never been a good witch. The raw power at his fingertips is wild and volatile in a way that is more likely to set his kitchen on fire than do anything useful. So he does something desperate and profoundly stupid: he makes a deal with a demon.
Malik isn’t just any demon, he’s an incubus. He’s ancient, powerful, and endlessly amused by the blushing virgin who just bound their souls together with a promise he barely understands.
The deal works. Newt’s magic finally starts to listen, but only when Malik is close, only when they’re touching, and the deeper the bond pulls them, the harder it becomes to ignore what an incubus actually needs to survive. For a virgin tethered to a sex demon, “deeper” is a dangerous direction.