In a rash, revenge-fueled decision, Marybeth decides to join the most feared gang in America, Black Bullet. During her initiation, she proves herself to be an amazing fighter, the best that the gang has ever seen and she quickly works her way up the ranks to third in command. Black Bullet and Atomic Bomb, the rival gang, always fight for dominance, which never phased Marybeth--Bat, as she is known in the gang--until she witnesses a ruthless murder during a gang fight. Faced with her morals, she decides to stop fighting for Black Bullet. As third in command, she knows too much to simply stop fighting and she isn't old enough to drop out of the gang, so the leader, Trigger, decides that the only way to solve the problem is to kill Bat. As the building explodes with Bat inside, secrets come to light and the truth is found out; a truth that will rock Black Bullet, Acco City, and the whole world, all the way to the core.