she's only Angel who loves devil

In a very beautiful and grand mansion, and it's night time. Outside, it's raining heavily, and there's thunder and lightning. Inside the mansion, we'll see a stunningly beautiful girl, around 20 years old, wearing a black gown. She'll be hugging a boy, around 25 years old, who's very handsome and charming. His eyes will be shining like red rubies.

The boy will ask the girl, "Do you really want to stay with me?" The girl will reply, "Yes, I really want to stay with you." The boy will say, "You know that if you stay with me, your life will be in danger, and you might even die?"

The girl will respond, "I don't care. I love you so much, and even if I die by your side, I'm ready to accept it." The boy will be surprised, saying, "I never expected anyone to love me this much." The girl will affirm, "Yes, I love you, no matter what you are or what you've done."

As they hug, a flash of light will fill the room, and the boy will become unconscious. The girl will try to hold him, but she is unsuccessful . He'll push her away, and the girl looks at him, she'll see that he's unconscious. She'll think to herself, "Why did this happen to us?" and she screamed very loudly "lord". What happened with boy? Who is the girl and why she loves him so much? And why she called him lord ? Let know in this story.