I think the geezer is shown to be desperate enough to do something extreme and vile.
Maybe there’s a round two with jjk but ig maybe by the time he comes around, Dan will need to be in the hospital and the jizz master would have escaped
Like it or not people usually cannot change within such a short time and jaekyung’s habit of acting first and thinking later is true for almost everyone with anger issues.
It’s very realistic for him to keep lashing out like this for way longer. Even with therapy and everything people require years to gradually get out of these habits and mindsets. So expecting jjk to turn into a constant golden retriever top would be more weird.
Now onto Kim Dan, the boy has had a choice to leave, has left, should leave again. But the decision to come back has also been his own every time and obv he will come back again, unless you know, he gets freaking kidnapped by jumin.
But overall it’s your basic mutual obsession due to compatible mental health issues and childhood trauma.
They’re both somewhat obsessed with each other and they both trigger each other and their respective coping mechanisms. (Not denying that it’s toxic but it works and that’s why it’s so common)