The Smile Has Left Your Eyes

I'm racking my brains about the ending because I refuse to accept it despite the fact that it (sorta?) makes sense. I hate it, I honestly despise the idea of these two poor souls dying the moment they decided to fight through the pain for their happiness besides, what about Jin Gook? How the hell is he gonna cope with their death? On the other hand I do think the ending fits this story though. Maybe I'm reading too much into it but I feel like the whole drama proves over and over again that for every action there is an equal and opposite reaction and sooner or later you're gonna have to face the consequences ... hence the final tragedy. You'd think it comes out of the blue when as a matter of fact it's the direct result of many people's choices and mistakes interconnected with each other.