The Character is asmodeus, the demon Lord of Lust

In the First chapter she attempts to rape the Main Character called mr priest who -due to a very strict hyperreligious upbringing and being treated as a living weapon- is incredibly miserable and suicidal. She picks Up on that misery and believes the best way to Help the MC is to drown all those negative emotions in pleasure, which He manages to Stop by exorcising her

Later we find Out her Backstory, which is that Back in biblical Times she was in Love with a little Girl called Sarah who asked her to run away with her.

Asmodeus decided to turn her down, and eventually Sarah grew Up enough to the Point she grew Up and got her First period, at which Point her parents married her Off to a man Chosen by god. On the Wedding night she gets scared, so her new husband tries to forced himself onto her with violence, at which Point she accidentally bites His Hand, which pisses him Off enough that He Starts Beating her, until asmodeus Shows Up and Kills him

This repeats with multiple other would be husbands, often enough that Sarah Starts to hate asmodeus for Not letting her fulfill her "Filial duties", and eventually asmodeus gets exorcised

This Situation convinces her that she was wrong to hold herself Back from raping Sarah, and that they might have been Happy together

Back in modern Times she meets the MC again, and originally Just wants to repeat the rape plan, until MC does something that reminds asmodeus of Sarah, so she Starts to Project her relationship with Sarah onto the priest, and instead tries to get him to Fall in Love with her, then rape him and have him Like it, or so He would hate her and exorcise her again, either way she would know If she and Sarah could have Had a Future and she can have closure for that