Honestly speaking- I love the idea that they become doom together- That kind of ending would just be??.
Although I feel as if they won't meet in another life because as someone said (I can't remember who- I apologize-) Doom mentioned that "There isn't another life".
I feel as if they might do a Goblin (like the halfway mark of it) ending. They fall for each other, She breaks the contract and Doom dies and she lives with the pain of losing him before wishing to not remember him or smth like that. Then we'd skip to a few months later where she's just happily living without remembering who he was and then someone like him shows up as an author and she gets her memories back- Like there's a lot of plot holes but still-
I feel like with this drama they could most probably do a sad ending as well. Just is a sick drama pfft