After managing to capture Cornelia, Lelouch forces her to reveal what little information she knows of Marianne's murder, but the answers do not please him one bit. V.V. takes Nunnally to Kaminejima, and Lelouch abandons the Black Knights to rescue his sister. Without Lelouch, the Black Knights begin to lose ground to the Britannian Army. Suzaku follows Lelouch, leading to a final confrontation between the former friends.

Lelouch directs the Black Knights in a counterattack against the Britannian forces and recalls how he came to forget his past: after Suzaku arrested him and brought him back to Britannia a year ago, the Emperor used his Geass to implant false memories in Lelouch's mind. The new Knightmare Frame prototype Vincent arrives and wreaks havoc on the Black Knights. They collapse Babel Tower to retreat, simultaneously dropping it on Viceroy Carares and creating a road straight to the Chinese Federation Consulate, where the Black Knights escape to. Zero broadcasts his plan to recreate the United State of Japan. The Britannian military retreats, but the pilot of the Vincent, Rolo, is not so easily swayed. After arriving at the consul grounds, he confronts Li Xingke, revealing that he too possesses the power of Geass.

Lelouch is shocked that Sayoko has made him into a playboy. As he tries to work out a way to undo the damage, Milly declares Cupid Day, where any girl can become a boy's girlfriend by stealing his hat. Rolo and Sayoko help Lelouch avoid the female students trying to catch him. Alone, Lelouch and Shirley discuss recent events and trade hats. Elsewhere, Knight of One Bismark Waldstein informs the Emperor of a meeting between the princes and princesses about waging war against the Chinese Federation, where Schneizel decides threats and negotiation will work better than open war. Cornelia, determined to reveal the existence of Geass in order to clear Euphemia's name, confronts General Bartley, who begs her to help them, saying the Emperor's recent actions may destroy the world. While Suzaku and Lloyd discuss on the Guren, Nunnally visits Kallen in prison. Jeremiah arrives in Area 11 and uses his newly-acquired Geass Canceller on Shirley, restoring her memories of Zero's identity.

Rolo admits to causing Shirley's death; rather than blame Rolo, Lelouch blames the existence of Geass itself. In retaliation, he mounts an assault on the Geass Directorate, slaughtering every man, woman, and child within the stronghold. V.V. pilots the Siegfried in an effort to stop the Black Knights, but is defeated by both Lelouch and Cornelia. He escapes to the Thought Elevator, where Charles awaits, and when Lelouch follows he is transported to the Sword of Akasha. Meanwhile, Kallen and Nunnally discuss Lelouch. They are interupted by Suzaku, who, despite having been told that Shirley's death was a suicide, decides to interrogate Kallen using Refrain, in order to confirm his suspicion that Lelouch has become Zero again.

Lelouch and Suzaku fight for the sake of their promise, the Zero Requiem. Suzaku battles Kallen, while Lelouch confronts Nunnally, his biggest and dearest enemy.