Nunnally vi Britannia

Nunnally Lamperouge (ナナリー・ランペルージ, Nanarī Ranperūji), 14 years old (15 at R2), is 100th Empress of Holy Britannian Empire. She is Lelouch Lamperouge's wheelchair-bound younger sister. Her real name is Nunnally Vi Britannia (ナナリー・ヴィ・ブリタニア, Nanarī Vi Buritania). Her seiyū is Kaori Nazuka. In the English dub, she is voiced by Rebecca Forstadt. While her role is limited in the anime series, a spin-off manga entitled Nightmare of Nunnally focuses on her, depicting what would have happened if Nunnally had received Geass as well as Lelouch.

Character outline
Nunnally was born Princess Nunnally vi Britannia, daughter of Emperor Charles zi Britannia, and Empress Marianne vi Britannia. She was 87th in line of succession to the Britannian Throne. When her mother was assassinated, Nunnally was paralyzed by bullet wounds on her legs, and went blind due to psychological trauma of witnessing the brutal murder of her mother. Lelouch believes that she may be able to see again someday. After the confrontation between Lelouch and the Emperor of Britannia about the murder of their mother, both Lelouch and Nunnally were exiled to Japan as political prisoners. They then went on to live in Kururugi residence where she first met Suzaku Kururugi.

After Britannia invades Japan, Lelouch hides their identity and changes their surname to Lamperouge. They then seek help from Marianne's old allies, the Ashford family, who kept their identity a secret and allowed the two siblings to live in a building on campus to accommodate her disabilities. Nunnally attends Ashford Academy's middle school and is friends with Lelouch's classmates, particularly Shirley Fenette. She is very kindhearted and calls the Elevens "Japanese people".

First season
Nunnally's role in the first season is rather minor, serving as little more than motivation for Lelouch's goal of overthrowing the Britannian empire and creating a world where Nunnally can live in peace. She is kidnapped by V.V. near the end of the season, and Lelouch abandons the Black Knights in the middle of battle to save her. Not only is he unsuccessful in doing so, being captured by Suzaku en route, but his departure leaves his forces powerless against the well-coordinated Britannian forces, ending in their decisive defeat.

Second season
The second season reveals that everyone's memories of Nunnally have been erased, Lelouch's included. Everyone at Ashford Academy believes that Rolo Lamperouge is Lelouch's younger brother instead, and has been the entire time. After recovering his memory, Lelouch deduces that Nunnally is likely being held hostage by the Emperor, who would not hesitate to use his children to achieve his goals. As a result, Lelouch must try to maintain the masquerade that he has not regained his memories in order to protect her.

Nunnally makes her first appearance in the second season as a Britannian princess and the new Viceroy of Area 11. She still remembers Lelouch, though she is unaware of his identity as Zero. Nunnally has vowed to continue her late sister Princess Euphemia's will by reinstating the Special Administrative Region in Japan, sharing her and Suzaku's belief that the world can be changed in gentle ways.

After Kallen Stadtfeld is captured and sent back to Area 11, Nunnally has her transferred to a better facility and gives her a dress to wear in lieu of an ordinary prisoner jumpsuit. They strike up a conversation about Lelouch, which Suzaku interrupts. He asks to speak with Kallen alone, specifically using her prisoner number rather than her name, which Nunnally notices. She also suspects that he is lying about Lelouch to protect her. During a meeting discussing the redevelopment of the ghettos, she confronts Miss Lohmeyer on the burdens it places on the Eleven population, able to tell from holding her hand that she is downplaying the problems it will cause. She insists that it be rewritten until it does not do so.

During the second battle of Tokyo, Rolo and Sayoko are sent to retrieve Nunnally. Though Sayoko manages to commandeer the transport set to evacuate Nunnally, both are seemingly killed when they are caught in the blast radius of Nina's F.L.E.I.J.A. bomb, fired unwillingly by Suzaku when his life was in danger.

When Lelouch converses with Charles and Marianne in episode 21, it is revealed that Nunnally's injuries were orchestrated by V.V., who set her up to be a witness to the murder of her mother. Her blindness, which was thought to be psychological, was actually the result of Charles' Geass, done to protect her against possible reprisal by V.V. Charles then chose to send them both away, arguing that he was doing so to protect them from V.V., whom he felt he could no longer trust.

By the end of Episode 24, Lelouch manages to make his way onto the Damocles and confront her, Nunnally opens her eyes to greet him, asking if he will use Geass on her. When Nunnally refuses to give Lelouch the Damocles Key, he uses his Geass on her. Nunnally explains that Damocles will become a hated symbol among the people, allowing them to move forward once it's gone. As this is the same plan Lelouch has devised, only with himself as the symbol, he uses his Geass to force Nunnally to relinquish the key and uses Damocles to take over the world. Calling him a coward and a liar, Nunnally can only watch helplessly as Lelouch walks down stairs, preventing her from chasing after him. Two months later, Nunnally is a prisoner being taken to witness the execution of the U.F.N. leaders. When Suzaku, in the guise of Zero, appears and impales Lelouch on his sword, Nunnally can only watch in shock. When Lelouch falls near her, she takes his hand and realizes that he has sacrificed himself on purpose. Nunnally cries hysterically as her brother dies. Some time later, Nunnally becomes the Empress of Britannia and remains an important diplomatic figure with Zero (Suzaku) and geassed Schneizel by her side.

Nightmare of Nunnally
Nightmare of Nunnally features an alternate story to the Code Geass series with Nunnally as the protagonist. It is not connected with the television series.

After the so-called "gas release" incident in the Shinjuku Ghetto, Nunnally arrives in the ruins seeking the missing Lelouch. A disembodied doll-like energy life-form, Magical Device Nemo (魔導器ネモ madouki nemo), appears before her and offers her a Geass contract. Nunnally accepts and gains the ability to see "lines of the future" (similar to the Geass of Bismarck Waldstein, though more accurate than his). Nemo assumes an appearance resembling an albino Nunnally upon contract finalization, and the two of them come to share a single mind. Nemo's personality remains distinct from Nunnally, and is said to be an expression of Nunnally's unconscious anger and hostility.

Nunnally and Nemo find themselves "as one" aboard the mysteriously manifested Knightmare Frame Mark Nemo. Angered that Lelouch might have been killed or injured, they quickly destroy several enemy Sutherlands. In retaliation, Clovis la Britannia sends Jeremiah Gottwald, Villetta Nu, and a unit of Sutherlands to intercept the Mark Nemo. Using their now shared Geass, Nunnally and Nemo defeat the entire unit. Their attention turns to Clovis, but they decide at the last moment to spare him upon recalling Lelouch's wish for a peaceful world.

Nunnally awakens in her normal body and her first response is to violently deny her participation in the conflict she has just witnessed. Nemo suddenly appears before her, claiming to be "an alternate manifestation of the girl known as Nunnally,"  the manifestation of the darkness in Nunnally's heart. She states that as per their contract, she will now become Nunnally's knight and protector. Nunnally is the only one that can "see" Nemo.

Nunnally's Geass contract gives her and Nemo the shared ability to read "the lines of the future", a skill functionally identical to precognition. A red, bird-like sigil lights up in Nemo's left eye when the ability is activated. When combined with their Knightmare Frame, the Mark Nemo, Nunnally and Nemo are unstoppable on the battlefield, since every move is known to them beforehand. In the anime, this type of Geass is used by Bismarck, the Knight of One; however, his is slightly different, in that it only reads a specific person's "line", rather than that of the future in general.

However, there is a side effect to using the geass as shown when Nunnally is forced to be confined in a bed due to extensive use of her powers.