Riixti IS a girl, right? The first time i stumbled across your blog ages ago i thought she was a boy, then i actually found out she's a girl, but maybe I'm just reading things out of context, did that change or something or is she still a girl?
She's a girl, yep. ;D She often gets mistaken for a male both in and out of character, so by this point she's made a game out of messing with people until they just have to ask. Koorii and I have a running joke that even though Riixti and Ziatt form a heterosexual relationship, the traditional gender roles are flip-flopped, with Riixti as the masculine one and Ziatt as the feminine one. Female asura don't have obvious breasts, either, so that just makes it even more fun.
If it were up to her she'd just swim in the nude, but wearing swim trunks around others is just another opportunity to mess with people who don't know her very well!