Jungkook was your boyfriend you loved each other a lot, you two were inseparable always together.

But one day your parents forced you to marry a guy you didn't want to, and Jungkook saw it, he felt betrayed and angry, he cursed you to never reunite with your love as he sacrificed himself.

Him in his next life being born as a demon as he realized that he was the one you always loved and he wouldn't be able to reunite with you.