I thought Sangwoo wouldn't kill someone from his close circle of friends since it'd be too dangerous, so Ji Eun would be safe, but after thinking 'bout it, with his ego and reckless behaviour... I'm beginning to feel pretty negative about her future. Tbh, I don't like the girl but it's not like she should die or something... This wasn't a question, sorry hahahaha btw, all your analyses and your friends' are awesome! Thanks!
Sorry this is such a late answer! I’ve never doubted that Sangwoo would hurt Jieun because dude is an impulsive mess, and I also didn’t doubt she’d eventually be Bum’s victim. But I thought she would have it longer, being developed into one of the more important characters, perhaps kidnapped by Sangwoo and became his prisoner for a while, before Sangwoo’s manipulation takes its toll & Bum would kill her. A bit surprised with the sudden murder in chap 19, but I can’t deny that it worked in showing us the depth and scale of Bum’s trouble.