User blog comment:ScotsFox/Gender in Hetalia/@comment-44908319-20200428161021

There doesn't seem to be any specific reason, but male characters seem to be the more dominant ones while the female ones seem to be the dominated ones. This theory seems to explain why Hungary, Belgium, Taiwan, Monaco and many other characters are male. Maybe Hima was just showing implicit sexism :) I can't prove my theory though and it is highly probable that I was wrong. But this seems to be a theory that kind of makes sense since Hima is a male, and many female characters in the story really seem to be the dominated ones. Post it if you have other theories?