In a desolate and parched future Earth, Grey, a class C soldier is fighting to achieve his late sister's dream, to rise in the ranks to become a citizen. Along the way, he gets the reputation of a relentless warrior who leaves few survivors, even among his comrades. One day, he learns that his mentor, Red, has been captured by the enemy. Impulsively, he and his female comrade, Nova, go out without permission to search for him. In doing so, they start on a quest that would turn all their perceptions of their world upside down as they discover new enemies and hard truths.