Imagine after a few months of dating your girlfriend tells you she's a demon. You laugh a bit at first, but she takes you back to her apartment and shows you her true form, something horrific and inhuman, but stunningly beautiful. You think she's going to kill you, but she doesn't.
She tells you that demons like her, who are sent to earth, have more autonomy then those who live in the underworld. As long as she sends a letter back to her demon lord every night, and doesn't invite the ire of any gods, she's basically safe. You ask if she needs you to leave, she begs you to stay.
You don't sleep together that night. You're both to afraid.
You go throughout the city the next day asking people who you think might be able to help. Scientists, scholars, priests of every faith, warlocks and witches of every school. They all tell you the same thing, they tell you it's impossible for a creature like her to feel something for a human, that she's just going to use you, even if she tries to do good. They tell you that you only love her human mask, that you'd run away from her true form, but you've seen her true form, and it was terrifying and inhuman, but it was beautiful.
When you next come to her you keep things you'd need to protect yourself from her. A cross, passages from the Torah, a pendent of Thor's hammer, a small statue of the Buddha, any holy force you could think to keep her at bay. When you lay eyes on her again you feel like you're betraying her just by taking such protective measures.
She seems afraid. Humans have tried to hurt her before. You hold her for a momment, pet her head, tell her that everything is going to be ok.
When you sleep with her that she doesn't need to wear her human disguise. She only needs it when other people can see her now, you're safe. It would prevent her from feeling anything anyway.
When you embrace her true form it's like nothing else on earth. Something you can't describe. Something terrifying, and inhuman, and beautiful.
