THIS part honestly.
I don't mind a good villain/anti hero x MC story. I don't mind them being actually grey or villainous or doing bad things but when it comes to this, it just so much bad. People actually died and for a joke and he couldn't care less so even if we get a backstory, it is so futile yk. There is no redemption that can make this redeemable.
Having an understanding of saha more as a character is fine, uijin having unresolved feelings for him is also fine but them being romantically involved and having something just doesn't make sense nor do I want to see it.

I swear if uijin and saha developed a romantic relationsh- (╬ ̄皿 ̄)凸
Just NO