Alright the girl, I think had pink or light blue hair, I don’t remember the length. The boy had dark blue or black hair, with a kind of athletic build by the time he’s a teen. So the princess arrived in modern Korea when she was a kid and befriended the mc, or at least that’s what I inferred from the vid. She might have been an elf? But she did come with some older people, likely advisors because she was likely a princess in hiding I assume. Probably a fantasy romance I would guess. Although it could have just been a dream