The Barsburg Empire's Military Academy is renowned for training elites who secure victory for the empire. Academy students freely employ an ability known as "Zaiphon" in combat, with the specific type of Zaiphon available depending on the soldier's nature. Teito Klein, an academy student, ranks among the most promising soldiers produced. Despite being ridiculed by everyone for being a sklave (German for slave) with no memories of his past, he befriends a fellow student named Mikage. While preparing for the final exam, Teito uncovers a dark secret connected to his past. After a failed attempt to assassinate Ayanami, a high-ranking official who killed his father, Teito is imprisoned awaiting punishment. Wishing only the best for Teito, Mikage assists him in escaping. Teito arrives at the 7th District Church, where he is taken in by the bishops. It is here that Teito attempts to evade the grasp of Ayanami and the Military, so he can rediscover his memories and learn why he is the person capable of changing the fate of the world.