THIS. I truly believe Jisung was Cho-ah's one true love and they would've ended back up together if Mujin wasn't in the story. All he did 'wrong' was love Cho-ah and be a better person than Mujin and that's what got him killed just like that He didn't deserve it.
I felt so sad for uke but i think the ex of uke also had a tragic ending. He doesn't do anything wrong but got murdered.