After emerging victorious against an alien species known as Usurpers using combat androids called Neans, mankind colonized Mars and enjoyed post-war peace. Having fulfilled their purpose as soldiers, Neans became subservient workers and second-class citizens to humans. Requiring a daily dose of Nectar to sustain themselves, the androids depend on their masters for its supply of the drug. However, among this societal hierarchy lie Proto-Neans, independent specialized androids that can summon metallic exoskeletons with superhuman capabilities. Rouge Redstar is one such Proto-Nean working undercover for Aletheia, the government organization overseeing the regulation of Neans, alongside her human partner, Naomi Orthmann.