Don’t understand why her title is “emperor” and not “empress”. You might think i...

i mean it's fiction first of all. but if you want to get historical female 'kings' were a thing in europe because kingdoms often banned queens/empresses from ruling but not all of these kingdoms had rules against a women holding the title of king/emperor.

I mean when Hatshepsut, Nefertiti, and Cleopatra ruled Egypt and where called pharaoh not great royal wife/ female. People online even get annoyed when they are refered to as "Queens" since some even dressed and acted like men to be treated equal to there other pharaoh's. In China Wu Zetian was called emperor not empress. Jadwiga from Poland was called king. Nigeria also had a female king. The only example I can think of used the female type is that queen Victoria is called queen instead of king. I somewhat think it makes sense since I think of it as a female that becomes our president would be president not first lady. Oh also, some religions call females in high positions priests instead of priestess cause of the power dynamic each stereotypically has.I think the male term comes with the prestige and many women in the past ( Cleo as an example) wanted to fight against sexism and be treated 100% as there male counterparts. So if someone from far far away here hi queen so and so they might not realize she is the main figure head. The male term some what solidified it.

Your answer is interesting. When I referred to past European ruler, I was thinking of the United Kingdom queens (since there were several) or the Empress Catherine II from Russia. These are the most well known European female rulers outside of Europe. Since they existed, a webcomic artist willing to be accurate would most likely take inspiration from these rulers and not the one from their own continent.
I know from my experience that in the Korean and Chinese webcomics with the European-inspired Monarchy, there are some cultural inaccuracies : basically it happens when the author thinks that a tradition / concept in Asia necessarily exists in the Westen world. For example, the position of « concubines » which was not a thing in European monarchies (it disappeared during the early middle age).
Therefore, I assume that the choice of the word « emperor » in this webcomic is more of a cultural projection / innacurancy. From my understanding, no well known south-east female ruler could keep the title of queen or empress for them to rule. So, the author would think that it works the same way in other countries.