me too but really I get the sense the author is using the scenario to show that those gender roles are ridiculous. i hope, anyway :)
Not really, did you read the sequel/spin off to this? There is a character there who even after transforming into a girl still keeps their sexual orientation from when they were a boy.
In this one I think Mamiya always liked Kyousuke even when she was a guy. And he was always a special existence to her, even back then. This is how I interpreted things from the scenes in their back story.
That's what I got from it too.
I love this manga, but the strict gender roles make me cringe