Years ago, mysterious beings only known as kihei appeared without warning and overran the world. To confront this strange menace, the Twilight Academy was established to train students in black magic and how to battle the otherworldly invaders. Graduates of this school are no strangers to death and many meet their doom while fulfilling their duty to protect humanity. Kou is just one more casualty in this war for survival...or so he thinks. Before he can even appreciate the fact that he’s still alive, a kihei pledges her loyalty to him and vows to stay by his side until the end of days, setting off a chain of events that can only lead down the road of madness and chaos.