What an original title.
Anyways, this was a nice little one-shot, a bit odd for a kid to be so aware of and accepting of the older one's sexuality, but then again in this world nowadays I guess it wouldn't be TOO out of place.
Actually, children are the most accepting of different sexualities and everything else pretty much. They're usually too young to have developed the prejudices of their families and communities so they really only care about themselves and what they think is fun or interesting. So when someone tells a kid that their gay, the kid really doesn't care. This story made a lot of sense, because the kid hears that Aki-nee is straight, but sees that she isn't, and it confuses her. And the time that it's based wouldn't affect that. Children really don't give a fuck. Like that video "Run Like a Girl" where boys, who are not girls, and teenagers/adults run 'like a girl' that you would see in tv. Then the girls, aged 5-12 about, just book it like some track runner because they don't have that societal expectation ingrained in them yet. Prejudice works the same way. It's society. We aren't born thinking gays are weird, we're taught that. Of course a kid wouldn't care.
And the girl in the story is not 'aware' of it, as in the fact that it's a problem in society, she just sees that this older girl who looks cute is a liar. She doesn't see why Aki-nee should hide it, where an older person would obviously understand why it's taboo.