Heart of Gold (Nikke: Goddess of Victory FanFic)

When Earth had been invaded in an instant, the powers that be selected very few individuals who would one day defend the Earth in the far future and become the Hope of Humanity.
Their plan, however, hadn't taken into account a different kind of threat, where the rest of humanity had to fight to survive on their own without these so-called "Hope of Humanity." Instead, the last of humanity created tough fighting machines known as Nikkes, who were the ones who truly became humanity's hope.
Since the initial invasion, one of those Hopes has been awakened and brought into the Ark; a surviving underground civilization, where the remaining humans wait for the day they'd reclaim the surface.