Yeah, I wonder, too. I think it might have something to do with the grandmother, however. Maybe something happens to her after she comes back from visiting Ye Zi's apartment and he goes home only to be confronted by his father?
Spoiler
I have read the raws, but I don't understand the language, so this is just a guess. Ye Zi is adopted by the grandmother and grows up with Gao Hang, who is very protective of him. But everything changes, when Ye Zi befriends some gay-people. Gao Hang misunderstand the situation and get jealous. At this point he realises his feelings for Ye Zi, but think that it's impossible and therefore decides to leave. The cold act is probably jealousy, since he thinks Ye Zi sleeps around. And Ye Zi plays along with it, since he likes Gao Hang and doesn't want to go back being like brothers. If he acts loose, then he have a reason for making a move on Gao Hang.
Well, even if that's the reason Xiao Hang shouldn't care about something that has nothing to do with him.
Where is the raws?
I LOVE YOU SO MUCH BITCH!!!
I wonder why Gao Hang was so angry when they finally met again... Was it only because of the other night when he saw Ye Zi with others? Also I'm curious about the reason Ye Zi is acting in a more "confident" or different way than his real personality. It clearly pisses Gao Hang off...