Yule and Kyung-soo complemented each other. You could see from Dong-Hyuk's what if scenario that it would be unfair to Dong-Hyuk if Kyung-soo chose him as he was still fixated on Yule~
Sad but true kyung-soo diserved better
After all that theres no way kyung soo can forget about yule its like yule became part of him kyung soo has an illness now and the illness cald yule, yule washed kyung soo mind. all the characters should go to a Psychologist or a mental hospital because all of them and up mentally ill after all that
WHY KYUNGSO ENDED UP WITH YULE AND LEAVE DONGHYUK INSTEAD?! JUST WHY?!! I prefer he is not being with anyone or maybe with someone new