I have two ideas available right now. If you're interested in either, please message me. If you're kind of interested in one, but would like to modify it to suit your needs, message me and I'll work with you!
The Exorcist and the Incubus
(If you would rather that we swap the gender roles, so that I play the exorcist and you play a succubus, I would be delighted to roleplay that scenario as well)
There is a mansion in the countryside that is best avoided if you value your health. It was once owned by a foul man with a grand fortune and inhabited by a cabal of demon worshipers. The cultists all died or moved away, but the evils within remained. For the past few decades, all has been silent about this mansion, but a new roadway now travels nearby it. People have gone missing. County officials have blamed road conditions, vast and rugged forestland and potent undercurrents from a nearby river as possible causes for the disappearances. The church knows better. A demon lives within this house, and it has been claiming victims. It is time for an exorcist to clean this up.
Coercion, Seduction, Corruption: The exorcist has a purity of body and soul on her side. To defeat her, the demon must corrupt her honor to lessen her power.
Monstrous Aspects: Our demon may appear somewhat human, but he is going to have some different features, be they frighteningly elongated limbs, extra or missing digits, a tail or a bonus set of genitals. We can talk about what modifications you enjoy.
The Summoner's Pet
(Once again, we can easily trade who plays which character for this roleplay, so that you're in charge of the summoner and I'm in charge of the Demon.)
With decades of experience in summoning and banishing demons, our summoner has taken to calling up a succubus to serve him in his abode. He has her doing house chores, performing magic rituals and, of course, entertaining him in a way that only a succubus can.
While she plays the role of a submissive, our succubus is simply biding her time. She whispers soft suggestions into the summoners ear, hoping to corrupt him further, or convince him to break his bindings on her so that she can burst forth into the world untethered.
Servitude. At the beginning of our roleplay, our Succubus is going to be a servant to our summoner. Of course, these roles might change.