so here's my take:
I honestly think the ex really likes yoomin, but he prolly doesn't even realize it. I don't wanna overthink it, but I feel like something happened to him that's why he ended up with that mindset. he clearly enjoys the comfort yoomin provides, like being around his family, so he doesn’t really mind not feeling that "butterfly" effect.
I really appreciate how realistic this manhwa is. it's so true that in long relationships, the attachment doesn’t just disappear, especially when the breakup happens because ur ex just doesn’t see u romantically. it's way harder to let go of something like that bcs u can't really hate ur ex partner. I really hope yoomin gets the closure she needs so she can finally move on and be with hyundo hehe (ʃƪ^3^)