Code Geass: Lelouch of the Rebellion

After the failed Black Rebellion uprising against the Holy Britannian Empire, the Black Knights resistance group is powerless without their leader Zero. Lelouch, who lost his memory of his past as Zero, is living a peaceful life as a high school student. C.C. attempts to jog his memory and convinces him to become Zero again to complete their mission.

After the Holy Empire of Britannia conquers Japan and renames it Area 11, a Britannian student named Lelouch Lamperouge gains the "Power of Kings" called Geass from a girl named C.C. Lelouch uses his newfound power to become Zero, a masked vigilante leading a rebellion against Britannia to seek revenge.