You're part of the Royal family, but before you were born, your father made a deal with a demon to make him king... But in exchange... He would have to give his oldest child which is you, to this demon once you turn 18. Your father didn't hesitate on that deal

Now it's your 18th birthday, just as you were about to blow the candles... A purple haired guy appeared behind you

"ah, so this is the child part of the deal...?" Rui said nonchalantly and he looked at the king

"Yes, you may take them away." The king replied back, saddened by this