Michal:
It seems that according to contract two scenarios are possible: 1. the world ends (doom comes upon the world). 2. someone she loves most die instead of her. There is no scenario when only TDK dies, and the world doesn't end. Yet she clearly believes that this will happen. She even asks Myeol Mang if she can wish for other people to forget about her existence when she dies. Doesn't make sense to wish for that when all people will cease to exist just when she die. Am I missing something?
Up in episode 14 she is certain that myulmang will die if she breaks the contract cause she doesn't want to wish doom on the world. That is why she asks him "please make me love no one" to which he replies "i can't do that" to which she says " you said if that's a wish you could fulfil it but why aren't you fulfilling it now?" To which he replies "i need to save you".
This basically implies that MM can grant her this wish but then she dies and everyone else live (his family,friends) and him. But the sad part is he will never cease to exist even after TDK's family eventually die. That is why he wants her to break the contract so he dies and no doom is doomed on the world and she gets to live.
In episode 16 he comes back as a Human cause he was butterfly of the garden that basically died for it's favourite flower and turned into a fertilizer and bloomed into a flower. (Flower symbolise humans ) as per the diety.