@plipplop Mizuki seems between genders as this point. He's clearly enjoying parts of being a woman, but isn't sure he feels comfortable with that yet.
As for the physiological change changing impulses, the only one that would directly affect Mizuki's impulses would be hormonal. Hormones don't change gender identity or sexual orientation though (they have tried this IRL - it doesn't work).
The physiological changes DO affect how others will treat Mizuki, and that will make her consider her own gender from another angle, however.
TL;DR Gender is complicated, and sans the magic elements, this series actually captures some of the feelings of gender dissonance and of socially transitioning. It's not real, but it's not way off the mark either.