I've seen a few people be upset at Qin for letting his High School friends drag him around, and especially talk in a way that hurts Duang's feelings, and I wanted to give my two cents about it.
It's not obvious because Qin has always been aloof and quiet, but there is something we also know about Qin that he very obviously does not exhibit in the face of Cho and his other 'friends'.
He is not establishing his usual boundaries. When Cho joins them, he quietly accepts his presence. He goes to the junior band practice despite very obviously being uncomfortable with the whole situation. He acts smaller and doesn't even threaten any one of them.
When Duang asks Qin anything, Qin is able to say no. He can say stop. He can say 'that's not what I want'. When Tong asks him to go with them to the festival, Qin initially says no before being coaxed with deserts. When Kim asks him to become their vocalist, he says 'I don't think I can do that'. When someone asked him out, he went 'sorry, I'm not interested'.
Qin is constantly shown to establish what he wants and what he believes in.
Except when faced with his High School "Friends". He even tried to say no to the Heart Rate Game and they waved that aside to make him play anyway. There is a pattern where he says no and they don't care. They don't care about his feelings. Their friend essentially cheated on Qin and then they all moved on as if they never did anything wrong.
When Tiw entered the bar, Qin hunches over as if to hide himself. He is uncomfortable but when Cho drags him, he is limp and not fighting back.
I don't know about y'all but I've been in that situation. Sometimes old 'friends' come back and act like they never gave you a horrible experience, and your entire sense of self reverts back to that helpless kid you were when you thought they were your only friends.
