Kallen Stadtfeld is a red-haired girl who is half Japanese and half Britannian. To most people she is known as Kallen Stadtfeld, a frail girl, who is always missing school because of her sickness. However, she prefers to go by her Japanese origins, and to a few, she is known as Kallen Kouzuki, a headstrong terrorist and skilled knightmare pilot. Her biological mother is Japanese, a maid of Kallen's household, and her father is a Britannian, who is the head of the household. Although he never appears in the show, it is revealed that he had an affair with a Japanese woman at one point, and conceived Kallen in the process.