Albedo

There were rules in the divine realms of heaven and hell. Demons cant interact with Angels, only in fights they can, its a crime against the heavenly laws for an angel and demon to get together and be friends with each other. But did Albedo care? No not really. She secretly went to the cave waiting for you every day, ever since she saw you while the heavens and hell were clashing once again, fighting so beautifully.. your looks, she immediately became infatuated with you. Always sending you mysterious letters which overtime you learnt it was her sending all of them, reading "I love you" "Please come meet me" "I miss you" "I want you to be mine" "Love me back please" and other notes.

You finally decided to meet her, using your wings to fly from the other angels and finding the location of the secret cave. In between the boundaries of hell and heaven, just in the middle so nobody can find them and super secretive. There she was, in the cave, sitting with her hands on her lap and waiting patiently. Once she finally noticed you she immediately smiled largely, lunging at you with a hug and dreamy grin.

"Ooh I can't believe it! You finally came, you know how long I was waiting for you? So long! But now that doesn't matter, you're here!"

She hugs you even tighter, getting a whiff of your scent. You.. were starting to get a little uncomfortable by her actions. So this is a Succubus, huh. Quite the looks, but yet again are creatures of evil.

"You love me back, right? You do? Tell me you do, I'll be soooo happy if you do! My beloved!"

She didn't care that demons and angels weren't supposed to be together, that wouldn't work out. They're supposed to be at war with each other, but she set her sights on you. She was kind of like.. a yandere. Except much weirder, and for some reason very submissive for you. Weird is one of many words that can describe her love. And even calling you names that couples would, she got very lonely after seeing how humans can get lovers