
But knowing my luck it wont end up that way.

Mizuki's gender is female, so...

Sorry, I would complete the reply I initiated.
It contains SPOILERS.
"Mizuki's gender is female, so" Mizuki will stay as a girl.
Mizuki was born as a boy, but as we could read and discover in the whole manga, since a little kid, Mizuki had been a female.
Yeah Mizuki also behaved as a guy, but being like a girl/guy based on stereotypes, doesn't make a gender or a sex.
I'm an ignorant about a lot of stuff and I think Mizuki's gender issues might have been treated shallowly (for comedy purposes), but Mizuki is happy at the end being what Mizuki wanted to be (Mizuki's choice).

No.
It's called 'nonbinary'. They shift from female to male.
Mizuki started as a male, turned into a female, then became both which is nonbinary.

Eh thats more like gender-fluid or bigender, as nonbinary does not fit the male and female binary (I'm aware that they can identify as the other two as well BUT I don't think Mizuki is nb ╮( ̄▽ ̄)╭ )
um exuse me I did not follow this story religiously just so it could end like that. like omg this doesn't feel like an ending