Bella one of the Demon Overlords, (she oversees contracts) gets sealed in a human body. One that made a contract with another demon overlord (anonymous identity for now) before she gave her soul up in exchange for her wish.
Bella has history with the human world because before she lost her powers in the demon world and got weaker, she made a contract with a human who just so happens to be the ancestor of the Kings royal family (where her new body is from).
Bella's new body is an aristocratic lady who is looked down on, and she also originally- also had a cold relationship with her brother and father since her mom died. They also- unlike other noble houses don't have any "hero ancestors" but became nobles through hard work alone...
Im seeing where the confusion happens...i guess theres a demon king they defeat in the human world but a demon god and demon queen from the demon realm along with demon overlords...
could anyone give me a summary of the entire thing im quite confused