I know that Hiura does not see himself as a girl. But if you extracted Hiura's characteristics and projected them onto a real person, even if you didn't know the concept of being trans, or disphoria, even if this was the 4th century, it would be hard not to think that person would like to be a...
Try this mental exercise:
Imagine this manga was anonymous, so there is no author to be an ultimate ambiguity resolver.
Now, if you saw a character (Hiura) that:
-Likes dressing like a girl and presenting feminine
-Likes being perceived as feminine
-Likes things that girls normally like, such as...