To me it reads like Akiba is trying to deny dressing as a girl at all (because it's embarrassing, others might overhear it -> leading to harassment) and Oto responds with asking if Akiba then is not a boy at all (but a transgender girl, implied). Not sure if this is the intended reading though.[big picture]
I don't understand what the slip-up here is, is this a lost-in-translation moment or something?