Born to a noble family, Casey left home to join the Imperial Knights, taking a prized family heirloom, a bow called the "Divine Cannon", with her. Over time, she established herself as a distinguished knight and earned Alexei Dinoia's favor. During her time as a knight, she met Damuron Atomais, and ten years prior to the events of the story, the two fought alongside each other in the Great War. Near the end of the war, Damuron was injured in battle, and Casey died attempting to protect him, though her efforts went to waste, as he died shortly thereafter during the battle at Mt. Temza.