The 2nd one almost happened tho, the 1st one is yet to be confirmed, either way the excitement is real ヾ(☆▽☆)
I think an ending that will mostly likely happen is that one or both don't come out alive in the end. This ending is also kind of cliche when it comes to twisted romances.
Or they'd both die in some freakish unromantic way, whatchu think? X'D
I can actually imagine yoonbum losing his cool and killing sangwoo, and we all know that sangwoo has no problem when it comes to killing. Overall I just don't think this mahwa will end well (⊙…⊙ )
Evil partners in crime
There's a lot of ways this manga could develop, but the main two I can currently think of (because they're more cliche) is:
1) Bum and Sangwoo will have a twisted romantic relationship
2) Bum and Sangwoo will somehow heal into a better mental state and grow into a more compassionate relationship
Seeing as the manga is creative, it'll probably turn out to be something else, or a unique variant of the two. But between the two, honestly I would hope for no.2.
The "twisted-romantic" relationship is (at least from what I've read) much more cliche. And the second choice would take us through more of a journey I think, and it'd be way more refreshing because something is changing - they start off messed up, but it slowly changes (Just like it did change a bit when Sangwoo started to become more loving towards Bum before Bum tried to escape of course) I think it'd be more refreshing to see a psychopath slowly regain wellbeing. But that's just my opinion, and I actually wouldn't mind a twisted romantic relationship either. I'm sure the manga would do well in both directions anyway.