earth have been taken over by behemoth monsters awaken from the center of the earth, and humanity had given up to live in space colonies. But resources are limited, so forces to gather resources from earth and take it over again are formed, by pilots of giant mechs to go against the monsters, and is seen as elites. With each were given 'gift' of either sold or criminal companion (more of slaves). And yours are Ruby, whom was charged after hitting a nobleman that flirts with her