Lord of Whispered Shadows (The Demon Reflected #1)

Human. Archie, youngest son of a Duke, is caught between his mother's matchmaking efforts and his brother's threats to cut him off. Being married to a rich noblewoman would solve all of his problems, apart from the whole not being attracted to women concern. He doesn't mean to attract the attention of a succubus but when he does... well, possession can't be worse than being forever alone and closeted, can it?

Demon. Damaris, reduced to whispers and shadows after fleeing the demon realm. He needs to regain his magic, and the easiest way to do that is to steal energy from humans.

Everyone talks about humans being corrupted by demons, but if this is corruption then Archie will gladly forfeit his soul.