The Germanic Star-Empire had made their intentions regarding the home world of humanity perfectly clear to the Heavenly Domain.
"Earth is ours! If you want it, come and take it!"
That was really all there was to the matter. Naturally, the Heavenly Domain was both unwilling to wage a war with a nation of racist psychopaths who had no qualms about annihilating other races and species down to the last woman and child.
But nor were they willing to concede Earth, specifically their homeland of Greater China, to these "barbarians." Because of this, the Heavenly Emperor demanded that his younger sister Princess Wang Jia-Li stay on Earth as a diplomat to the Germanic Star-Empire and its stubborn Emperor.