I've seen the raw up to chapter 20 and it confused me when I saw someone who looks like Chiaki wearing a skirt. I've already guessed that Chiaki might be female because of that and her name(from what I know, it is a female name), but it's nice to finally get a confirmation(can't read Japanese).
The fact that Kaoru's crush is a into women, those curves of hers from previous chapters, and a slightly protruding chest (from this chapter, which I didn't notice from previous chapters) says it all. The restroom part just confirmed it.
So saotome was a girl....kinda had a feeling about it cuz her face and hair were very girly in my opinion. Sure she is tall, flat chested (or binds her could be big tiddies to look like a guy) with broad shoulders and not very feminine when talking but if you pay attention to her face...you can see the girly shapes....
Still think kaoru should just come clean to his mom about who he really is tho... sure she will try to kill herself or kaoru instead...probably....but if he intends to be happy...