
Ok so I re-read it, and it's possible for him to have a happy ending.
If the flashback he got (from when he passed out in chapter... 14? Around that) was real, and he actually had a family -- then it's possible for him to stay there.
There was a theory that Seong-ah had a brother, and if that brother theory is real - and that brother is already dead, then it's most likely that he'll be able to stay there.

No matter how much you deny it, jaekyung saved Dan from poverty, saved his grandma, did so many requests for him, and defended him --
I'm not justifying his actions, he's still a big asshole - but it's not like he has no hope this will sound like an excuse, but he doesn't know how to express it / have anger issues, ... Or read social cues - but it's not as bad as everyone's exaggerating him to be.
Anyways I'm just hoping that he develops into a green flag soon, there's no erasing of the past but he better apologize atleast

I think Dan's too kind, and he'd probably think that he'd be betraying "Jaekyung" -- since he paid for everything, and was introduced to his grandma as a friend
BUT YEAH U GUYS HAVE A POINT WITH DAN'S PROBLEM
He could probably be used to the kind lifestyle, and sees things differently since he grew up with his grandma - that's why he's blind to red toxicity :(
I love mephisto so much he's probably like the most decent one out of all of them -- plus the instinct part probably isn't his fault either, but the tentacle monster's that occupied his body..
ANYWAYS HIS HANDS ARE HOT. THE NAILS???? THE CLOTHING DESIGN??? And ok his dick might be disgusting but ???? Hello?? It's mephisto come on (I wouldn't want that near me tbh but
not gonna lie his nails actually slay