???

Exactly what I’m not understanding
So he should cut hangyul’s thread connected with blondie or kill blondie…to get Hangyul’s brother…what

Yep, bc he can't get a lover due to bad karma (divine punishment) for having done too many bad deeds. To solve that he needs to make up for it by doing a a good deed, and cutting the thread connecting hangyul and blondie (without killing blondie) is a good deed because it's a fake, cursed thread made with dark arts, which would eventually get blondie and hangyul killed (since the evil spirit that made that connected thread will eventually ask them to pay the price, which is hangyul and blondie's lives). If he can't find a way to cut the thread, then option 2 is to at least save Hangyul alone, by killing blondie.

He probably thinks Hangyul's bro would be grateful to him saving Hangyul, no matter how he does it (and if Hangyul tells his bro all about him seeing ghosts)

Thanks for explaining
I couldn’t put this together lol