In the "Geass Route" ending, Kallen was in the hangar tuning her "Guren" and was approached by Rai who wanted to talk to her. When Rai revealed that he's leaving the Black Knights, Kallen was shocked and demanded a reason from him. This led to Rai telling her that he has an illness and doesn't know how long he has left. After hearing this, Kallen ordered him to cure his illness and return. After Rai had left the hangar, Kallen turned to her "Guren" and slammed her fist in anger and sadness.