Battle of Mt. Fuji

Background
After Lelouch's actions at the Tokyo Settlement, which resulted in Lelouch taking all the UFN representatives hostage, the Aerial Fortress Damocles is first unveiled, obliterating Britannia's capital city, Pendragon, with a F.L.E.I.J.A. strike.

Adding to Lelouch's trouble, Schneizel reveals that Nunnally is alive and well, and she declares herself to be Lelouch and Suzaku's enemy, leaving Lelouch despaired.

Nevertheless, the Damocles advanced through Japan on its plotted course to the Yellow Sea, from where it would ascend into orbit and into a position to target the whole world at once. However, Lelouch decided to take the fight to Schneizel, bringing the full might of the Britannian Military onto the Damocles with its escorts, including The Black Knights, as it was passing over Mt. Fuji, Japan.

The Battle
The battle went on uneven odds, as Damocles fired multiple F.L.E.I.J.A. warheads onto the Britannian ranks, battle turning into wholesale slaughter. After seeing that F.L.E.I.J.A.'s detonation could not be prevented by destroying the warhead, Lelouch orders all units to spread their ranks and fall back, and that went for Avalon, too, - even with its Blaze Luminous shielding, it was too dangerous to expose his flagship. Schneizel also decided not to target Avalon, as there were hostages on board.

As the creation of the F.L.E.I.J.A. Eliminator was underway, Lelouch remotely detonated the Mt. Fuji' Sakuradite mines. resulting in a volcanic eruption which decimated much of the Black Knights forces, including Ikaruga, which downed near the mountain and was subsequently evacuated. However, Avalon is also damaged and forced to land, with Lelouch leaving the ship aboard his Shinkirō, already fitted with a F.L.E.I.J.A. Eliminator. As he does, however, the Black Knights' boarding party, led by Li Xingke aboard his Shenhu, boards the Avalon, proceeding to rescue the hostages. After F.L.E.I.J.A. is disabled mid-flight, Lelouch creates an opening in Damocles's Blaze Luminous, allowing Lelouch and Suzaku to board the station, Gino trailing after them and destroying the Shinkirō, before being defeated by Suzaku. Suzaku, however, challenges Kallen on her Guren S.E.I.T.E.N. in a duel outside the Damocles. As a result, Lancelot Albion was utterly destroyed, and the Guren severely damaged. Meanwhile, Jeremiah Gottwald defeats Anya Alstrem aboard her Mordred, but uses his Geass Canceler on her instead of killing her.

When aboard, Lelouch proceeds to take the majority of the Damocles' personnel under his Geass. Afterwards, he fools Schneizel into believing that he was on the command deck, surprising Schneizel when he arrives into his almost-launched shuttle instead. Lelouch uses his Geass on Schneisel, making him serve Zero.

One obstacle is then left in Lelouch's path - Nunnally, who holds the key to the Damocles, and has been launching the F.L.E.I.J.A.s. She regains her sight, breaking Charles's Geass, and asks Lelouch if he would use his Geass on her to obtain the key. He proceeds to do so, taking the key from her and gaining absolute control over Damocles' destructive power.

Outcome
With the Damocles in his hands, Lelouch declares himself the ruler of the world. In the remaining two months, the remnant Black Knights are rounded up, and repressions and pacifications of the conquered world begin. After the time skip, the Zero Requiem concludes.