The Humans lost AU! Sans x Slave! Abused! Dragon! Reader

Everything was amazing in the world. Unlike the world we live in today the world had changed its 4019, only 7 islands remain on the world. The most habitable being the large island of Recoshi. The others being only habitable by animals or hybrids. But all that came to an end months later when monster were released onto the surface. Monsters were welcomed with opened arms to the islands. The king and his daughter made sure of this, but some monsters did not get along with humans and some humans did not get along with monsters. The kings and Queens of monsters reasoned with the King. The monsters wanted some of the Islands to call their own but the King only said no. It was not a debatable subject but it was the first fight monster and humans had many fights that soon ended in another war. The kingdom so use to the peace they had lived in did not know how to fight back but many tried. Soon The kingdom was ruled over by monsters making Humans and Hybrids their Slaves or pets. But what happened to the loyal princess and her father.