Kallen Stadtfeld, who prefers to be called by her birth name, "Kozuki Kallen", leads a double life as a meek and fragile Ashford Academy student, and as a member of the Order of the Black Knights by Lelouch Lamperouge. She use to live with both her Britannian stepmother and biological mother who was employed as a maid, but her happy life was shattered when her biological mother was arrested for using an illegal drug known as Refrain.
I've read that the seiyuu for this character, Koshimizu Ami, had a difficult time voice acting Kallen because of her double life. It makes you realize what a hard life this character must lead in the anime. Great cosplay though! It looks like she even considered the location of this photo shoot... A good choice, I might add.