There's some Klaroline stories where Klaus meets young!Caroline and this is how I imagined Klaus saying goodbye to her.

Klaus: Caroline, I need to go. It will be dangerous for you if I stay. But even with me gone I want you to remember something... I love you and that will never change. I love you for Always & Forever.

Young!Caroline: No! You can't leave me! What will I do now? Without you... Please stay...

Klaus: I can't. I'm sorry, love. But I will return to you, love. Please don't ever forget that I love you. My love for you has no bounds. I will return to you as fast as I can. I love you with all my heart.

Young!Caroline: No... I love you, Nik. You're my favorite person in the world. I don't want you to go.

Klaus: I know, Love. I know... But I promise you this. I will come back to you. And until then keep being the extraordinary girl you are. You will have a great life and when I'll return I will want to know everything.

AN: I know this was sad but I really enjoyed making these gifs and I hope you like it.