MY PREDICTION : Kihoon sunbae tried to forcibly connect their string of fate during middle...

MY PREDICTION : Kihoon sunbae tried to forcibly connect their string of fate during middle school, he probably snapped out of it or something happened that made him feel ashamed that he couldn’t look at Yeon in the eyes that’s why he suddenly rejected him and found himself a “girlfriend”. Then this whole thing happened, he’s happy that they’re connected by the quest but deep down he still feels guilty because he thought Yeon’s actions and feelings are only caused by the red string of fate that he forcibly connected years ago that’s why he couldn’t accept and cried from guilt. He probably thought he had taken away or stolen what could’ve been a normal love life for Yeon due to his selfishness.