Responses

Right!!! Exactly as you said, he's Fake Nice!!!!! He had the audacity to ask for a second chance when he couldn't even deny the reason Yumin left him. If he was given the chance, he wouldn't change, he'd just be like he was but just a little honest because he has no choice, Yumin found out on her own!!
He's story and backstory didn't make it better. I am asexual myself, but I will never trick anyone just because I want them for myself. I know people crave romance and sexual attraction, and if what I can give is not enough, I let them go, easy as that.
He, on the other hand, like Yumin said, he didn't tell her what he was feeling. He maliciously said what he was trapping Yumin into, to his friend, OVER THE PHONE—what's more insincere than that? And when Yumin confronted him about what he said, he didn't deny it, instead, he tried to make excuses (his excuses would have been sweet if he told Yumin truthfully). If he learned to be a decent person and if he truly cared about Yumin, he would have told her from the beginning, and he could have tried to woo her in his own ways from then on. What a fucking asshole.