@kronix
It can't be NTR, because they're not in any kind of real relationship. You can't forcibly engage two people against their will. That's dumb. The whole idea is dumb, and it's clearly dumb even in Korea with all their weird customs. "Well I promised my friend!" Boohoo, so fucking what? Those two old farts can marry each other if they want to join families that bad.
I feel like there must be a translation error in this as well, when he's like "We can't be engaged, we're not married yet"... engagement happens before marriage and ends when a marriage takes place.
So if he doesn't want to date her , and she wants to date her new boss (although hellooooo sexual harassment lawsuits in the U.S., by the way) then that's just hunky dory. No one is in a relationship with anyone else, they're all free to make their own choices.