On August 10, 2010, a.t.b., Japan was conquered by the Holy Empire of Britannia. Seven years later, teenage student Lelouch Lamperouge finds himself pulled into a battle between anti-government terrorists and the Britannian Army in the Shinjuku Ghetto. In the midst of the conflict, a mysterious, green-haired girl saves him from death by granting him "the power of the king", which allows him to compel others to do his bidding.

One year after the Black Rebellion, Lelouch Lamperouge has resumed his normal school life with no apparent memories of the year before. After skipping remedial gym class, he sets off with younger brother Rolo to gamble at Babel Tower. Led by C.C., the Order of the Black Knights launches an attack on the complex to retrieve Lelouch. C.C. reawakens Lelouch's memories, and he resumes his identity as Zero. Suzaku Kururugi declares to the Emperor that he will personally kill Zero.

Suzaku returns to Ashford Academy to investigate Lelouch. With the Black Knights reassembled, Lelouch plans to lead the resistance while maintaining his façade as a student. A welcoming party is held for Suzaku at the academy, and C.C.'s love of pizza threatens to reveal Lelouch's secret; Kallen arrives to retrieve her but is seen by Villeta. She tells Lelouch how she came with Kaname Ohgi the previous year, and Lelouch uses this information to blackmail her. Alone, Suzaku reveals to Lelouch his goal of becoming the Knight of One, which would allow him complete governing authority over Area 11. To test Lelouch, he allows him to speak with the new Viceroy of Area 11: Nunnally vi Britannia.