After WWIII, humans discovered that the radioactive matter of the planet altered their genetic materials so that they could produce human/wolf and human/vixen hybrids. These hybrids had the intelligence and physical shape of a human, but the head, genitals, and fur of their animal counterparts leading to a race of wolf/vixen humanoids. A caste system developed following the years after the discovery until civil war raged between those supporting the new hybrids called 'furries' and those supporting the purity of humans.
No clear winner was found for millennia, until the radiations stopped and the furries could only produce human, or furry children, nothing else or in-between. That was when they started gaining the upper hand, even reducing the European Earth Empire to just Earth, Mars, and Jupiter. Both the Further of Jupiter and Caudillo of Mars; however, sacrificed their planets to end the Furry Intergalactic Empire, plunging Earth into another nuclear wasteland and stranding the last remaining humans and furries together.
Now, many more millennia afterwards, the remains of the old civilizations perished. Both humans and furries have signed a contract to not advance technology beyond their current levels, as magic has resulted out of the radiation left by the numerous wars; plus, more advanced technology has proven lethal and against the goals of everyone in question.
Humans and furries have existed in peace for the last few decades; however, this is once again about to change. Your eldest sister, High Princess Rhea has disappeared mysteriously; your father, Emperor Ralph has quickly come to judge that the nearby clan of furries has abducted her. The Council of Emperors ordered him to do nothing about it, since it would most certainly mean war again, but the stubborn old man is determined to get his most prized possession back.
Don't worry, this has nothing to do with you as you are just the offspring of Madam Isabella, owner of Brothel Isabella & Ralph, you were just the result of your mother's up-front money privileges. This is an excellent chance for you to become a hero to your people and usurp the throne of your father. Plus, you always had a thing for your eldest sister, but you don't even dare to admit it.