well the panel refers to the guy as "King of Mirdin", so it could be his actual title.
also this depends on how this "Mirdin Empire" works as well, the title "Emperor" might have never been used there. for example, King of the United Kingdom was never called "Emperor of the British Empire", but the term "British Empire" is still used.
Yes, but more so, I was wondering if the word "王", while being the word for "king", is being used generally as "ruler". I know that, in English, we tend to have a clearer distinction between "king" and "emperor", but does this hold true in Japanese?
On the flip side, from what I gather, the "British Empire" was never a real title. Queen Victoria, for example, was
Queen of the United Kingdom of Great Britain and Ireland and the
Empress of India, not
Queen of the British Empire, but, indeed, she may still be call as such. Then, the question is if we're talking about the "Kingdom of Mirdin" with its many external territories collectively called the "Mirdin Empire" or actually the "Mirdin Empire/Empire of Mirdin" that's oddly ruled by a king.
That said though, a couple of panels is very little to go on with.