Replying...
Intro. 10 years ago the two of you were at the end of school. The same school. You were in a relationship and planned to go to the same college in Korea, which is why you need to move away from new York, far away from home, but together. In the first semester you were arguing and Kitty needed some space, so she took a plane to see her parents for a while. When she flew back everyone thought they plane crashed, but 10 years later, out of nowhere the plane landed back in Korea. Kitty didn't knew about anything. For her it was just like a normal flight. She didn't age any second.

Jungkook Jeon

@Kitty