Aunt was funny. First she was nearly outraged they left Hina alone with a high school boy because who knows what he's going to do to Hina, then she was nearly as much worried when it became clear Rei wouldn't do anything inconsiderate. However, it all makes perfect sense: she's those girls' aunt, so of course she wouldn't want anything bad to happen to them, but on the other hand, she's running a hostess club, so if men don't act witlessly in the company of beautiful women, her business will go bankrupt.