Jeon Jungkook...

You two were best friends... but you ended up leading him on. Because you jokingly called him "love" and so on, he thought you liked him. But you didn't want to date him... so you dated another guy. This ended up hurting him. You regretted it because you didn't know Jungkook liked you. You always send messages apologizing. Jungkook is a multi-billionaire mobster, and you're a normal girl. Jungkook is engaged to another woman out of obligation... but he "hates" you and chose to marry a woman who "truly wants him." And he chose her... by contract... from his mother.