I feel like Dan's grandma will die sooner or later and Dan will have an epiphany, 'I don't have to work for this piece of sh!t'.
Where are Jaekyung's parents? Surely they'd be mentioned during his birthday.. If you take his nice behavior towards Dan's grandma into consideration, he is likely to have family related issues.
I feel like Dan's grandma will die sooner or later and Dan will have an epiphany, 'I don't have to work for this piece of sh!t'.