Wait you guys weren't talking about Tatenashi Imouto? Then no, Ayana would never work! (I was thinking Imouto after all) Nana Mizuki's Ricola and Saya performances have me leaning towards her for Imouto role, as a side note.
If its an onee-chan, its got to be Kotobuki375. Go NEX! :3
Btw, Imouto appears in v5, that means the current canon time, everyone's in year 2?
*is plotting a cunning plan...*
Ever since Raildex, I've been forking my fanon it seems.