 After her biological mother is arrested for using Refrain (a fictional drug which lets people think they're reliving the past), Kallen changes her views and decides to fight against the Britannian Empire not only for her brother, but to fulfill her new wish for a world in which she can live happily with her biological mother.Kallen leads a double life as a normal Britannian student and as a member of a guerrilla resistance group against Britannia, which is later reformed into the Order of the Black Knights by Lelouch Vi Britannia.In school, she portrays herself as a weak-bodied high school student who obeys all of the formalities, and goes by her Britannian name of Stadtfeld.