The Swedish Empire had kings, while Japan had emperors. How is it? What we call the Swedish Empire was never technically a real empire. Just one that has many different races and conquers territory

The Swedish Empire had kings, while Japan had emperors. How is it?

What we call the Swedish Empire was never technically a real empire. Just a kingdom with many different races and conquered territories. I think the main reason Why Sweden doesn't claim to be an empire is that they have these in other territories:

These include the territories of Bremen-Verdeen, Wismar and Pomerania. These were part of the Holy Roman Empire, and even though Sweden won these in the 30-year war, having two emperors in the HRE was not yet complete. Technically, you don't even have a real king other than the ruler of the Empire. Prussia has an exception, as long as they call themselves the King of Prussia and not the King of Prussia, note that it refers only to areas outside of Thera.