@criver @Umesan @mendics @Deoxyribo9
I feel like I should clarify a few things
As it was pointed out, because of the names and how they're written, you can't tell by just them.
I don't really read much genderbender, so idk how much it matters but to me the fact that Jun talks like a male (using the male "I " and shit) and Kaoru like a female is a pretty strong indicator. Also if you look at the title pages of the last few chapters, kaoru is always portrayed as female and Jun as male. In ch6 when they're not it is written "male?" below Jun and "female?" below kaoru.
Personally I think the running joke is that kaoru is a better male than Jun, and vice versa, which also kinda leads to the confusion.
However, in chapter one, both do things without realising that could suggest the opposite. Jun doesn't realise he did his nails, and kaoru forgets to sit with her legs closed. Also before this kaoru says, "did you wash it, talking about my uniform" and then later Jun hands her a male uniform. Also at ch2 Jun ends up using the weird perfume thing to attract women; the list goes on.
Bottom line, their personalities and the way they act makes it super ambiguous as to what their original genders are, and without going into some deep interpretation about gender identity and shit, the pronouns and the way they talk are the only leads we have really