The ending is i think the female lead is not real human, she kinda a being created from time machine paradox or something like that ? basically in the end she die but somehow by the paradox things she kinda reincarnated to another 18 years old girl, the male lead was sad of her death, he grow beard and looks messy, he just passed the reincarnated female lead and suddenly she feels sad and crying, then she run towards male lead who just passed her, the end.