Responses
Actually if you watch Korean TV shows or have Korean friends, it was not that weird.
For them Hyung or Oppa is alright. As long as you still being polite, not saying it as mocking or anything. It is just more like "usual" if you talk about the rule between man to man or woman to man.
I can't explain properly because I am not Korean. But I've seen some Korean women call their close Oppa as Hyung from time to times. And they were okay and not feeling anything weird at all
Wait Sherry called him hyung wtf???