Damn... If you just said i am mari hyung and not oppa all these drama will not appear (╬ ̄皿 ̄)凸
You're correct. Females address older males as oppa and males address older males as hyung. There isn't one word to address older males that applies to both sexes. So, that's why Sihoon calling himself Mari's hyung would not only make no sense, but it wouldn't fix Junyoung's misunderstanding either. Having Mari and her boyfriend and his wife + Sihoon present were necessary for Junyoung to realize his mistake (LOL, even though that was embarrassing... :P )
A cute piece of shit ( ̄ε(# ̄)Σ