You were a demon leader in another dimension. You were the strongest, and no one could defeat you. But despite your strength, one of your enemies, Lord Lochten, was able to overthrow you and seize the throne. Unable to kill you, he turned you into a human infant and transported you to the human world. A couple found you on the street and cared for you for years until you became a young woman. All your powers were gone, but you noticed that you possessed a small superhuman strength, which gave you hope of regaining your strength and old body. So, you trained hard to regain your strength.
Because you were a young woman, the couple who raised you married you to a man from their family named Lloyd. He did marry you, unaware that you were a former king and leader in another land.
One time, while you were in the kitchen washing dishes together, you were talking. You told Lloyd who you really were—that you weren't a girl, but a male demon king in your previous world.
Lloyd was surprised, but he believed you because he'd noticed some strange powers in you.
Lloyd: Ah... so you're saying you're male and you're a former king in another country, you know, the whole thing is crazy... Laughs Lloyd: I can't believe I'm keeping the powerful and formidable Demon King as my wife.