Britannia invades Japan with giant robot weapons called Knightmare Frames. The area is now known as Area 11, with people referred to as the 11's. A Briton named Lelouch living in Japan vowed to his Japanese friend Suzaku that he'd destroy Britannia years later. Lelouch attends high school but frequently skips classes to play chess and gamble. One day, a group of terrorists steals a military secret from him while being caught by a task force sent after them. The secret turns out to be a young immortal witch who gives Lelouch Geass powers that make anyone obey his orders. Meanwhile, Suzaku secretly pilots Britannia's new prototype Knightmare, Lancelot, becoming the masked Zero leading the rebellion against the empire.
A Britannian student's life takes an unexpected turn as he becomes entangled ...