So the protagonist is forced to part with a love interest for supernatural reasons. But it's okay! Because at the end of the story they meet a person from the real world who happens to look exactly like the person they lost. Usually it's never explained why this person looks exactly the same, but it's a quick way to turn a Bittersweet Ending into a Happy Ending. If time travel is involved, the love interest in the present is often an Identical Grandson or grandfather, which also makes for some incestuous implications if you assume they get married and have babies.