For a K-drama ending, it was decent. K-dramas never know how to end themselves. Always rushed and plotholey endings. I'd say it was one of the better ones, maybe there will be a better explanation in the special.
Haha, I just saw your comment now. I'm still sad about this drama, 2 years later basically. But a lot of cool dramas have come out since then. Currently found my favorite drama of all time. (We will see how it ends), Cinderella and 4K :D