
This is gonna be a spoiler, so yep.
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For me, it's more like he got more attached to YoonBum. (which could be fucked up depending on anyone's interpretation) In the next chapters, Sangwoo will even bring YoonBum to the mall and will text his friends that he'll bring someone to the upcoming festival.
YoonBum, as expected, is developing Stockholm Syndrome. When they were at the mall, he had all the chance to escape, but he kept on looking for Sangwoo.

Thank you for this !! I bought the raws and was wondering what that text.said lol
I really think that in ch6 when sangwoo leaves the house, at that point, he was legitimately scared that yoonbum would leave him because he started to feel he had some kind of mental support.
This is one of the rare times I was actually upset that the victim tried to escape. Not because I didn't actually want him to, but it ended up undoing their relationship that was finally becoming somewhat safe. Sangwoo felt deceived and betrayed and went back to being next level fucked up. I wanted both of them to become better, but.... well let's see how it goes.