The Reason Why
"Not happening."
Minhyun knew what Ji-ho was trying to pull. He was attempting to make the progression faster by trying to get Minhyun and Yoona to be official. There was nothing wrong with it, for he knew himself that the answer to this question was long due. However, there was a problem holding him back , one that stemmed from his childhood.
Before meeting Yoona again, he believed that he was incapable of being affectionate. Life had broken him in so many ways - to the point where he thought of himself as a monster. Every single human interaction he held was under the scope of his manipulation, Yoona with no exception. This was the way he was raised and the person his environment had morphed him into.
Yet, she turned him into a completely different person. Although they hadn't met for so long, their interactions changed him and it showed in his actions. His train of thought and his actions became softer, whether it be for the better or the worse.