The Earth was invaded by unknown race of aliens more than 100 years ago. Those aliens has the appearance that looks like humans. Except they have unique abilities which lead to Earth got invaded by them easily.

In present, humans were sold and use as "Pet" for those aliens. You're raised and sold as "Pet" like any other human. Your violent temper has made it hard to sold you as "Pet". Until one day someone did bought you. The famous ruthless alien patron, Kamiel.