Kallen Kōzuki

"Snap out of it, Lelouch! You're Zero now! You have an obligation! You have to live up to the dreams you once gave us all! So please, keep fooling us until you no longer can! We need you to be Zero this time with all your heart. Play your role like you mean it!"

- Kallen Kōzuki

Kallen Kōzuki (紅月カレン) is one of the main characters featured in Code Geass: Lelouch of the Rebellion, as well as one of the two protagonists of Code Geass: Lancelot & Guren. She is officially known as Kallen Stadtfeld (カレン・シュタットフェルト), and goes by this name at school, but prefers her mother's maiden Japanese name during her revolutionary (now military) activities.

Ami Koshimizu won "Best Actress in supporting role" for her role as Kallen at the first Seiyuu Awards in 2007. Kallen was awarded 8th place in the 29th Anime Grand Prix, then 17th and 16th, respectively, in the following two.

Appearance
Kallen is a young woman who has a slim yet strong build, and fair skin. Her most distinguishing features are her big blue eyes and her red hair, which she had combed down at school but spiked up when fighting or in her own privacy. She has an average height, being slightly taller than C.C.

When she is fighting in her original Knightmare, an outdated Glasgow, Kallen wore a vest-shorts combination. Once she begins to pilot the Guren Mark II, she wears a magenta suit that zips up to her neck. Other times, Kallen is seen wearing a standard Black Knights uniform.

In school, Kallen wears a ladies' school uniform. While at important reunions or during her brief time as a prisoner, she wore a yellow, fashionable dress to an elegant blue dress.

Personality
Kallen is a strong-willed, determined, loyal and brave individual who can also be quite short-tempered, forceful and somewhat impulsive. Despite her tough attitude, Kallen is actually quite sensitive, compassionate and truly gentle, however after the death of her brother she doesn't show this side much anymore. Her brother's death has also affected her relationship with her parents, though over time Kallen begins to renew her relationship with her mother, and like her brother, she becomes one of Kallen's reasons to liberate Japan. Her relationship with her father, both before and after Britannia took over Japan, is never elaborated on, though she did refer to him as "dad" on one occasion, implying that their relationship is (or at least was) probably positive.

While being both Japanese and Britannian, Kallen had the ability to live a normal life. However, she refused to fully accept her Britannian side as it would mean abandoning her Japanese friends, people, and self; thus making her one of the few selfless characters in all the series. On multiple occasions at the beginning of the series, she had claimed that she hates Britannians, though that was clearly an exaggeration as Kallen has been seen caring about Britannian civilians on multiple occasions, a prime example being her visible concern for the Student Council during the Lake Kawaguchi incident. Her character arc can be summarized as thus: she transforms from an emotional, somewhat prejudiced, untrusting girl in a tawdry rebellion into a confident, capable fighter with a much stronger sense of justice and morality, willing to put aside her feelings and interests to protect those she loves and cares about.

At Ashford Academy, Kallen was forced to hide her identity in order to avoid suspicion, which caused her to change her hairstyle and her true personality. Whereas normally Kallen is powerful, confident, willful, and Japanese-favoring, at school she was a milquetoast, withdrawn ill girl who didn't speak up very much (the ill part was to hide her recreational activities as a Black Knight). In spite of this, she was welcomed fondly into the Student Council, which becomes a significant factor in her character development. However, when she fell under suspicion, Kallen often readied the knife that she conceals in a small pink pouch, showing what she would do to keep her identity secret. After finally changing Britannia's political system and gaining liberty for Japan due to Zero and his closest allies, Kallen begins to show her true feisty nature as her school while still being a member of the Black Knights.

In battle, Kallen is aggressive (this could be due to the fact that her weapons are mainly-close range), often ruthless, and very opportunistic. Her code name, Q-1, is a shortened version of the "Queen" on a chessboard, the strongest piece in a chess game. She is very confident in her Knightmare piloting capabilities as well as her own abilities and rightfully so - her Guren annihilated most of Cornelia's forces during the Battle of Narita, and could even defeat two powerful Knights of the Round in later battles. However, despite being one of the very best pilots in the series, if not the very best, she is not indestructible; as shown by her eventual capture in R2.

Character Outline
Kallen is a young Britannian-Japanese woman, who believes herself to be Japanese at heart and prefers to be known by her Japanese mother's name. Her mother is an Eleven who stayed with her children for most of their lives. Her brother, Naoto Kōzuki (紅月ナオト, Kōzuki Naoto), with whom she had a deep connection, was a former leader of a resistance organization before his death. After his death, Kallen became a member of the same guerilla resistance group against Britannia, which would later be reformed into the Order of the Black Knights by Lelouch vi Britannia several years later.

Her father is a Britannian noble who comes from a prestigious family, and since his legal wife, Mrs. Stadtfeld, could not bear any children, Mr. Stadtfeld requested Ms. Kōzuki to formally adopt Kallen into his household as his heir. Since her daughter would benefit from being a Britannian noble, Ms. Kōzuki accepted his request without Kallen's consent, much to her displeasure. Though Stadtfeld's wife ordered her never to see her daughter again, Ms. Kōzuki refused, fighting hard to be hired as a maid in the Stadtfelds' household in order to remain by her daughter's side, something that Kallen was unaware at that time.

Both Kallen's stepmother, and mother live with her in the same house, but her biological mother was often mistreated by both her stepmother, the other maids (who were all pure Britannians), and even Kallen herself after their relationship became strained, though she would try to discreetly help her mother at times but still stayed away from her. Since then, Kallen attends the Ashford Academy, where she is a member of its student council and is one of its most outstanding students, though she skipped school regularly as a result of participating in terrorist activities with an excuse of poor health.

Code Geass: Lelouch of the Rebellion
Kallen appears early in the first episode, driving a truck with C.C.'s capsule, and attempts to fight off Jeremiah's Purist Faction using a Glasgow. After Lelouch gains possession of his Geass from C.C., he takes possession of an enemy Sutherland and helps Kallen to escape the other Knightmare Frames chasing her. He further directs the remaining resistance forces, granting them a decisive advantage until Suzaku Kururugi uses his Lancelot to disable their Knightmares. She sacrifices her own Knightmare in return for helping her earlier against Jeremiah to allow Lelouch to escape, despite not knowing who he really is. She is able to escape after ejecting, meeting up with Ohgi and the rest of the resistance. However, the Britannian Military found where they were hiding. When the commander was just about to issue the order to fire, the Viceroy, Clovis la Britannia orders a ceasefire saving Kallen and the others.

After this incident, Kallen returns back to school for the time being. She returns back to class with a fake persona of a frail girl. After Lelouch discovers that Kallen, one of the terrorists he helped in Shinjuku Ghetto, attends the same school, he attempts to confirm his suspicions. Lelouch's unfamiliarity with his Geass however, causes him to reveal knowledge of the Shinjuku incident to Kallen, leading her to suspect him of being their unknown benefactor. As they both plan on exposing the other's suspicions, the Student Council throws a party for Kallen. During their explanation as to why allows Rivalz to propose a toast. Shirley stating that they are too young for it, causes Rivalz to throw the bottle to Lelouch. With Lelouch having the bottle, Shirley attempts to retrieve it from him. However, the cork pops open spraying all over Kallen. Kallen then takes a shower and uses this situation to her advantage in order to find out if Lelouch really is Zero. Lelouch creates a cunning deception to ease her suspicions of his identity by playing a recorded message of himself on the telephone with the help of a Geassed Sayoko, drawing her suspicions of him. When the death of Prince Clovis is announced in the media, it is Suzaku who is accused of the murder.

After receiving the message from Zero, both Kallen and Ohgi decide to help him save Suzaku Kururugi who was falsely accused of murdering Clovis. Both have their doubts as the operation is going, but Zero uses his own strategy and his Geass to turn the situation in his favor resulting in them believing in Zero.

Arthur, a stray cat, is later chased throughout the school grounds by the entire student body after wandering into the Lamperouge residence and escaping with Lelouch's Zero mask. Milly announced that the one who would catch the cat would get a kiss from any member of the Student Council. Suzaku and Lelouch were the ones that got the cat and got a kiss on the cheek from Nunnally. The Student Council adopts him and builds a cat house in the council room. Following this incident, Kallen along with the rest of the student body watches Prince Clovis' funeral on living. During the funeral, the Emperor of Britannia makes a speech on the virtues of inequality and the social battle for evolution and betterment.

Following Lelouch's failed attempt at stopping the new viceroy of Area 11, Cornelia li Britannia, the Japan Liberation Front decide to act and in turn kidnapped Britannians in a hotel jacking. Unable to stand by, Zero decides that this event can be the starting point for a new organization. After saving the hostages, Zero uses the media in order to publicly announce the formation of the Black Knights with the core members present.

With the formation of the Black Knights and Zero's increasing number of victories over the Britannian forces, Kallen comes to greatly admire him. Later on, Kallen is seen back at her house and for the first time is shown her step-mother, Mrs. Stadtfeld and as well as Mrs. Kōzuki who has become a maid in order to stay with her daughter. During one of the Black Knights operations to stop the distribution of the drug, Refrain, Kallen notices her mother as one of the people using it. She attempts to save her using her Glasgow, but a corrupted member of the Britannian police force uses a Knightpolice in order to kill Kallen. Kallen then ensues in a battle with it and eventually defeats him. During the battle, Kallen realizes that the reason her mother decided to stay in the Stadtfeld household was to be with her and calls herself a fool for not realizing her mother's love towards her. Later, at the hospital where Mrs. Kozuki is taken for treatment due to the aftereffects of Refrain, Kallen informs her mother of her sentence for Refrain usage and promises her that she will take part in making a world where they can both live happily together.

After losing her Glasgow, Zero gives Kallen the newly-developed Guren Mk-II to replace it. As Zero decides to attack Cornelia in the Narita Mountains, all members of the Black Knights head to Narita. Kallen starts off the operation using the Guren's Radiant Wave Surger to start a landslide that will decimate the Britannian forces. Afterward, Kallen effectively starts to destroy the remaining forces including most of the Purist Faction. She easily outmatched Jeremiah and dispatched Kewell with ease as well. She then moves on to her next checkpoint which is to trap Cornelia. She initially has the advantage and overwhelms Cornelia until Zero arrives to talk with Cornelia. As they prepare to capture her, Suzaku appears with the Lancelot in an attempt to save the Viceroy. Zero enraged that the Lancelot is again interfering with his plans orders Kallen to destroy. Kallen engages in a one on one fight with Suzaku having an advantage with the Guren. As they continue fighting, Suzaku is shocked at the power of the Guren but is unwilling to give up. He fires a shot from his VARIS which in turn Kallen attempts to block with the Radiant Wave Surger. However, the ground beneath her gives away, causing her to fall and damage her Knightmare. Because of this, Zero orders all Black Knights to retreat leaving the JLF to fend for themselves giving much discomfort to Kallen, Ohgi, and Tamaki.

Before the Black Knights begin their operation to rescue Tohdoh from his scheduled execution, Rakshata appears to meet Zero and give them the new Knightmare models and suits. Kallen goes along with Zero to retrieve Tohdoh. After reuniting with the Four Holy Swords, Suzaku appears once again with the Lancelot in order to stop them from leaving. During their fight, reinforcements appear causing Tohdoh to issue the command to release the chaff-smoke which Kallen does so and retreats. Now that the Black Knights are growing, Zero announces the chain of command and gives Kallen the position of being captain of the Zero Squad which is Zero's personal force. Hearing that Suzaku is appointed Euphemia's knight, the Black Knights decide on what his fate shall be because of his rising popularity with the Elevens. Diethard decides to take his own course and hints to Kallen to assassinate Suzaku in order to please Zero. She attempts to assassinate him during his party but is interrupted by Lelouch.

Afterward, she is seen during the battle at Shikine Island in order to capture Suzaku. The plan goes wrong when Schneizel appears with the Avalon and fires at Zero and Suzaku with the Hadron Cannon. Later, Kallen appears to be alive and is found by Suzaku who arrests her for being a member of the Black Knights. They spent time together discussing their life as well as Ashford until things became heated talking about their ideals only to be shocked by the truth of Genbu's assassination and that Suzaku is willing to atone for it. The following day, Kallen and Suzaku run into Zero and Euphemia. The floor below them collapses giving Zero and Kallen a chance to escape with the Gawain.



At the end of the first season, Kallen reveals her identity to the students of Ashford Academy when the Black Knights occupy it as their base of operations, convincing the student council that they will not be harmed. When Zero abandons the battle to rescue Nunnally, Kallen follows him. She witnesses his confrontation with Suzaku and learns about his true identity, the truth about the massacre of SAZ, and his Geass power. She was also shocked to hear that Lelouch admitting that he used the Japanese, including her, for his scheme. She flees in shock rather than aiding Lelouch to deal with Suzaku.

Code Geass: Oz the Reflection
Following the Black Rebellion, Kallen had fled Japan with Urabe and had not yet reunited with C.C. after her battle with the Siegfried. The two had hidden in Gujarat a state in the northwest part of India. During this time, her Guren's destroyed Radiant Wave Surger arm had been replaced with that of a Gloucester. Orpheus had been given a mission by Rakshata to deliver specialized equipment for their Knightmares to use, including a replacement arm. However, the group is attacked by a Britannian Military group, the Blue Barons, and they fight off the group together.

Code Geass: Lancelot & Guren
During the incident at the Special Administrative Zone, unknown to Kallen, she saved Benio Akagi from death.

Sometime later, Kallen returns to Japan and is given room and board at a harbor inn, and meets Benio Akagi. That same night, Benio warns Kallen that the owner of the inn plans to sell her out to Britannia. Thanking her, Kallen says she'll tie her up to make it look like she had nothing to do with it, though Benio says she would like to come with her. Though Kallen refuses, she tells Benio if she wants to help, that when the time comes, to head for Tokyo, though she doesn't elaborate on what she means. Kallen then fights off the Britannian Knightmares that come for her Guren hidden in the inn's warehouse.

Code Geass: Lelouch of the Rebellion R2
One year later, Kallen is still part of the Black Knights but due to revealing her identity has had to leave Ashford Academy. The memory of her was one of those erased from Lelouch's mind by Charles zi Britannia, although the other students are still aware of her existence. Along with C.C., she is one of the first members to know Zero's identity and secret power, having been brought up to speed by C.C. in the interim. Kallen is first seen disguised as a bunny suit-wearing prostitute/waitress at Babel Tower where Lelouch is planning to gamble. She ends up bumping into Lelouch while serving drinks, and indirectly says she forgives him for what he did by quoting him. She tries and fails to put a tracking device on him and catches the eye of a mafia boss. Lelouch, out of generosity, decides to play a game of chess over Kallen, but after Lelouch wins and C.C. invades the tower, Kallen reveals herself and defeats all of the mafias with ease. She then grabs a confused Lelouch's hand and tries to run off with him, but Rolo uses his Geass on her and takes Lelouch back, forcing Kallen to spend the rest of the mission in the Guren Mk-II.

During the operation to kidnap Nunnally vi Britannia as she is being transported to Area 11, Kallen receives an upgrade for the Guren Mk-II, giving it flight capabilities and an upgraded radiation arm. With it she is able to destroy Guilford’s Vincent and the remaining two Glaston Knights flanking him, then incapacitate Gino and Anya’s Knightmare Frames with a wide-range burst. Her battle with Suzaku is cut short when the airship carrying Nunnally crashes into the sea.

After this incident, Lelouch becomes depressed over Nunnally's involvement, since he can't bring himself to go against her wishes. When he nearly resorts to taking Refrain, Kallen steps in and talks him out of it. Still somewhat depressed, he tries to kiss her, but despite her feelings for him she backs out at the last moment and slaps him, insisting that he bears the responsibility for realizing the dream he gave the Japanese people. After Lelouch regains his composure and tricks the Britannians into exiling the Black Knights, she asks him why he came back. Instead of answering, he asks her to come back to Ashford Academy with him once their mission is finished, but is interrupted by C.C. before he can explain why. The two grew closer afterward.

During the Black Knights attempted kidnapping of Empress Tianzi, Kallen is captured by Li Xingke in his Shenhu, having taken her Guren into battle, with Tamaki failing to do maintenance also failing to replace its energy filler. Lelouch visibly stunned, swears that he'll rescue her, though Diethard Reid suggests abandoning her as a casualty of war. Touched by Lelouch's words, Kallen calmly waits for him. After the High Eunuchs turn to Schneizel el Britannia for military support, she is turned over to Suzaku along with the Guren. She is sent back to prison in Area 11 and subsequently transferred into a more comfortable solitary cell by Nunnally. She is even given a dress to wear. Suzaku approaches her after Shirley's death, intending to use the drug Refrain to find out if Lelouch has become Zero once again, but cannot bring himself to do it because he refuses to stoop to Lelouch's level. In retaliation, she beats him severely during their next meeting when Suzaku tries to apologize.

During the second battle of Tokyo, Kallen is rescued from captivity and returned to the Guren (complete with a pilot suit brought by Sayoko). Using the new Guren, she decimates the Britannian forces. Luciano and the Valkyrie Squadron are killed, as are an untold number of support units. She then fights Suzaku, easily breaking through his defenses and bringing him to the brink of death. In doing so, however, she activates his Geass command, forcing him to survive by firing the F.L.E.I.J.A. bomb. She dodges it and the bomb hits the government building, destroying a fair portion of the Tokyo Settlement.

After Kallen returns to the Black Knights and Zero's identity is revealed, she tries to defend him. When the others won't listen, she asks what she means to him, expressing a willingness to die then and there as long as it's with him. Lelouch, thinking that he had lost everyone he held dear to him refused to have her die with him and lies and calls her a tool, but then whispers that she should live on without him within earshot. She unsuccessfully tries to get the Black Knights to wait after their first attempt to kill Zero fails thanks to Rolo, and is left standing on the hanger floor when Rolo uses his Geass to escape with Lelouch leaving her and the Black Knights shocked as she had the similar experience at Babel Tower. After Lelouch's escape, Kallen tries to protest how Ohgi and the others have discarded Zero so readily despite all that he has done for them, but they refuse to listen, still angered at the idea that they were merely being used as pawns. As the Black Knights move to assist with stopping the rebellion within the Emperor Charles' forces, Kallen thinks to herself that Lelouch needs to live, as she cannot move on before getting an answer to her question. When Lelouch is crowned the Emperor, Kallen and the rest of the Black Knights are visibly stunned.

Following Lelouch's declaration that Britannia will join the UFN, Kallen escorts him to the meeting, giving orders to the Black Knights beforehand to gun her down if she appears to be under the influence of Geass. Lelouch gets her to take the long route, giving them the chance to speak in private. Kallen recounts their history, then asks Lelouch what he intends to gain by becoming Emperor, as well as what she means to him. Lelouch remains silent, so she kisses him to show her feelings. When he doesn't react, she bids him farewell. Lelouch does the same once she can no longer hear him. When Lelouch takes the UFN leaders hostage Kallen feels betrayed and hurt, insisting that she'll take Lelouch down personally, as she possesses the only Knightmare capable of fighting Suzaku's Lancelot Albion. Li Xingke however, orders her not to fight, fearing for the safety of the hostages.

After the Black Knights side with Schneizel, Gino agrees to fight despite that he would be going against Britannia, telling Kallen that he understands her feelings a little. Kallen is stationed in the front lines. She breaks away from the mainline to try and reach Lelouch but is called back. When Lelouch detonates the Mt. Fuji Sakuradite mines, Kallen and Tamaki shield the crippled Ikaruga from being destroyed by its crash landing. Kallen breaks into the Avalon and attempts to kill Lelouch, with tears in her eyes as she does so, but is stopped by C.C. Kallen easily defeats C.C. and, with the help of Gino, proceeds to the Damocles for a final confrontation with Suzaku.

After a fierce battle, Kallen manages to land a decisive blow on the Lancelot before losing consciousness. Gino rescues her while the Lancelot explodes. After the battle, she is taken along with many others who rebelled against Lelouch to be publicly executed, where she witnesses Lelouch's death by Suzaku disguised as Zero. Understanding Lelouch's plan, she screamed helplessly as Lelouch was stabbed. However, she still stated with Tohdoh that Suzaku was "Zero."

Two months after Lelouch's death, Kallen has forgiven him since she understood his plan completely. She narrates the changing world thanks to him. She is living with her mother in a Japanese town who appears to have recovered from refrain addiction. Kallen still attends Ashford Academy since Lelouch wanted her to return there, but has thrown away her frail cover, signified by her going to school with her true hairstyle and the Guren's key around her neck while still a member of the Black Knights. She keeps a photo of Lelouch in the center of her picture wall in her room, smiling at it before hurrying to school.

Kallen's character poem "Yuukyou Seishunka" that came with the Code Geass Complete Best CD reveals she had fallen in love with Lelouch through her devotion to him and that if he had told her that he loves her, even if it was a lie, during their scene together at turn 22 where she asked him what she meant to him and why he told her to live on previously, she would have "followed him to hell". Knowing that she would do precisely that was the reason Lelouch remained silent, as he wanted Kallen to live on. She then declares that it wasn't just because of that she fell in love with him.

In Turn 25.01, Kallen gathers at the rebuilt Ashford Academy with the remaining, former and current members of the Student Council. That's when Suzaku (as Zero) and Nunnally stops by and greets them. Her feelings were also hinted in Code Geass R2 Miraculous Birthday where the Student Council members experience Lelouch where she tried to make Lelouch praise her. At the ending, she cried, "Idiot, now I can't forget you even when I want to!"

Piloting Skills and Battle Prowess
Kallen is an extremely skilled Knightmare Frame pilot, rivaling the abilities of even the Knights of Rounds. She is acknowledged as the ace pilot of the Black Knights by enemies and allies alike. Her codename, "Q-1," references, in algebraic Chess notation, the Queen piece, the most powerful piece in chess. In Lelouch's assessment of the core members of the Black Knights, her "Combat Ability" score is 100 out of 100, matching that of Kyoshiro Tohdoh. It should also be noted that she was able to defeat Cornelia's personal squad, and later to the Knight of Ten, Luciano Bradley. She even could fight with the Knight of Zero, Suzaku Kururugi, on the same level even with his "live on" command activated. With the strong blasts and energy shots from the radiation arm of her Guren Mk-II, Kallen can take down almost any Knightmare Frame in a single attack should they allow her to make physical contact, apart of restraining their attacks with the strings of her Slash Harken projectiles and blocking their attacks with her fork knife by striking them down. Later models also have numerous secondary attack modes for mid- and long-range combat such as several improvements of its former weapons like more powerful explosions, while also gaining the Energy Wing System which gives her four wings which can act as shields, projectiles, and blades. Her Knightmare Frame is also incredibly fast, allowing her to fight on the same level as some of the most advanced Knightmare Frames in the series, and later also gaining the ability to fly at high speeds.

Outside of a Knightmare, Kallen displays superior fighting abilities at both armed and unarmed combat.

High Intelligence and Leadership
Kallen has shown high resourcefulness in battle, being able to see through her opponents' plans and usually takes advantage of their first mistakes or doubts in order to defeat them while making effective counterattacks. She also is apparently quite knowledgeable at academics since her grades in school are top of the class despite her frequent absences.

After passing more time at the Black Knights, Kallen has shown to be a good leader to her own squad's subordinates and even can be diplomatic to others while making plans at negotiations or tactics.

Lelouch vi Britannia
Her relationship with Lelouch becomes one of the main focuses in her character development, no doubt assisted by the complexities of their relationship and their numerous similarities. While on one hand, Kallen initially disliked Lelouch Lamperouge due to his arrogant, seemingly-indifferent attitude to his surroundings and possibly due to the fact that everyone around them thinks they're dating, even to the point of slapping him on occasion. On the other hand, Kallen holds a strong admiration and loyalty towards his alter-ego, Zero, due to his leadership and his beliefs in justice, which along with her impressive battle skills and her own ideals, gave her the position of his right-hand woman along with C.C. After it is revealed to her that Lelouch and Zero are one and the same, Kallen believed he chose to use both her and the Japanese through Suzaku's words. However, Kallen learns in time that Lelouch's true intentions are noble for a more peaceful world with a stronger sense of liberty, and thus she slowly develops feelings for him whilst simultaneously protecting his identity. Her loyalty towards Lelouch has been tested throughout the series as such when she was willing to die with him instead of living and betraying him, as well as when she still retained her feelings for him even after he faked to be "the enemy of the world" (something unknown for her at that time) but opposed him because of the injustice he was causing but she was hesitant while trying to kill him. After realizing his true plan and finally forgive him, Kallen was the only other person besides C.C., Nunnally, and Suzaku to shed tears for Lelouch and chose to remember him not as the enemy of the world but as the man she loved.

Benio Akagi
According to Kallen, she says that if she had a younger sister, she imagines their relationship would be like the one between her and Benio. Noticing her talent during her training, she stops Kagari from ending the mock battle when it seems she is on the losing end to Tamaki. When Benio volunteers for the Zero Squad, Kallen gives Benio her old Knightmare, now the Burai Custom. When Benio is overcome due to the emotions she feels after taking her first kill on the battlefield, Kallen is the one to help her and tells her to hold on to those feelings, because she isn't some mindless machine.

Code Geass: Lelouch of the Re;surrection
During her first appearance in the movie, Kallen is seen with Lloyd and Sayoko while they are being pursued by soldiers from the Kingdom of Zilkhstan, Kallen was shocked to see Lelouch alive, she even cried with hugging mindless Lelouch by thinking past. Later on, in the movie it was revealed Schneizel sent Cornelia li Britannia with a small number of troops to monitor the region while sending Kallen Stadtfeld, Lloyd Asplund, and Sayoko Shinozaki to infiltrate Zilkhstan for information. Together alongside Lelouch and C.C she was able to help rescue Nunnally.

Lost Colors
In the video game spin-off, Kallen is one of the potential love interests. She asks to meet Rai in a hot spring. The rest of the student council comes in while they are talking, resulting in Kallen trying to explain the misunderstanding. Kallen eventually walks out.

In the Black Knights path, if Rai stops Princess Euphemia from following through with Lelouch's accidental Geass command (an alternate version to episode 22-23), Kallen shows a great deal of gratitude toward Rai for saving the Japanese. Afterward, Rai and Kallen continue to be faithful members of the Black Knights. It is even hinted that she likes Rai. Further more members of the student council and the black knights even noted how close both Rai and Kallen are and just asumed that both of them are dating and are poorly hiding it.

Code Geass: The Manga
The manga differs from the real series focusing on the Black Knights activities, in the manga Kallen is not present during C.C's appearance. Lelouch's first meeting with her is also different as she bumps into him at school. She is in love with Zero but despises Lelouch.

Kallen protests at the school rather than at the settlement. She is also apparently Zero's only soldier as only she helps him, such as when they rescue Suzaku. She shares the same relationship with Lelouch in the anime with her admiration for Zero and dislikes for Lelouch. It also hinted that she has a crush on Zero due to her extreme reaction when she thought Zero had come to save her. Also, she was not with Ohgi and the other resistance members until the Black Knights are formed. She later finds out that Zero is Lelouch when he runs up to meet up with him and the other Black Knights at the Government Bureau to take over it only to be stopped by Suzaku and similar to the anime, she abandons him learning everything from Suzaku.

In the second part of the storyline, she helps Lelouch regain his memories of C.C. and Geass with the help of C.C as a food cart worker instead of a bunny girl. She meets Lelouch at Ashford Halloween party not the second annual school festival about her loyalty as well as helping C.C escape due to obsession with pizza. She does not get captured and is with Zero the whole time until the betrayal. She kisses Lelouch during Britannia's entrance to UFN. After Zero Requiem, she narrates to him about how the world has changed.

Nightmare of Nunnally
Kallen and the other Resistance members took advantage of the arrival of Nunnally's Mark Nemo Knightmare Frame to make their escape from Britannian forces pursuing them. When Kallen escapes from the rooftops after she was taken hostage with the other student council members in a hotel at Lake Kawaguchi, she witnesses the arrival of the Mark Nemo.

Suzaku of the Counterattack
In the manga spin-off, Kallen becomes a member of the Black Knights after Zero forms the organization but has doubts about his methods after a Black Knight faction had gone renegade and orchestrated an attack, taking the lives of nearby civilians, including Lenard Lubie.

When Zero is planning to attack the Britannian Art Gallery with the goal of assassinating the Emperor who has arrived there, Kallen confronted him about whether it would be a trap and also commented that she would still follow him. Admiring her answer and loyalty, Lelouch placed a Geass command on her that if anything would happen to him then she would lead the Black Knights. When the Black Knights took the Art Gallery hostage, she is confronted by Suzaku and was surprised that she's not only a member but a half Britannian-Japanese right after he left to stop Zero from killing the Emperor. After Lelouch was captured and accused of killing the Emperor, Kallen assumes leadership of the Black Knights as the new Zero and later leads the remaining Black Knight members to begin an assault on the Governor Building of Area 11, unaware that Lelouch is freed by Suzaku and are both planning to stop Schneizel.

Five years later, a 22-year-old Kallen is seen walking on the street and still a member of the Black Knights and in contact, but while she was passing by, she suddenly saw someone who looks like a 17-year-old Suzaku, which she thinks she's imagined it.

Nunnally in Wonderland
In Code Geass: Nunnally in Wonderland, Kallen plays the role of the March Hare. While Nunnally is at the White Rabbit's (Anya's) house, Kallen storms in, demanding to know who is causing all of the noise, which was caused by the Cook (Nina). During this time, she ends up fighting the White Rabbit to determine who should be the only rabbit in the forest, with both of them using carrot-like objects in a fashion similar to the weapons used by their respective Knightmares. Their fight ends up causing Nunnally to leave the house, much to Lelouch's anger, since he wanted them to be more hospitable to Nunnally. After Nunnally leaves, the March Hare, the White Rabbit, the Cook, the Duchess (Milly), and the Dormouse (Rivalz) realize that they are missing the Mad Hatter.

Super Robot Wars Z2
Kallen makes her debut as the Red Devil of the Elevens and fights Chirico from Armored Troopers Votoms and loses. Her manager Kolin betrays her and she and Chirico team up to fight him. She ends up in an arm-wrestling match with Kamina from Gurren Lagann since they both have mechas named Gurren. Ester, Crowe's disciple, idolized her and formed a friendship with her. She helps Lelouch when Heero and Wufei try to kill him.

Granblue Fantasy
Article in Granblue Fantasy Wiki.

Shadowverse
Kallen is an optional leader for Bloodcraft decks.

Trivia

 * Her Japanese surname, Kōzuki (紅月) means "Red Moon" in Japanese.
 * "Kallen" (American name) meaning "Pure". "Karen" (Japanese name) meaning "カレン・シュタットフィールド", which means "beautiful as a lotus flower"
 * Kallen's plushie's name is "Tabatacchi"
 * In Lelouch's assessment of the core members of the Black Knights, Kallen has the highest Loyalty with 100 of a 100.
 * "Q-1", the codename given to Kallen by Zero is in reference to the queen, the most powerful piece in the game of chess. A fitting name as Kallen is the Ace of the Black Knights and his closest ally aside from C.C.
 * In an interview reported by the anime magazine Newtype USA, Seiyuu Ami Koshimizu talked about the difficulty of voicing Kallen because of the double life that her character had. Certain aspects of Kallen's character such as her girlish naivete and competitiveness made it easy for the voice actress to relate, even to the point of admitting that in some ways they act very much the same.
 * As a running gag, Kallen ends up naked or immodestly dressed in front of other people on numerous occasions: Lelouch sees her naked after she pulls back a shower curtain in surprise in the third episode, Suzaku sees her bathing under a waterfall when they are stranded on Kaminejima Island, she is forced to dress as a Playboy Bunny at the start of the second season, and she walks in on a meeting between C.C. and the Chinese ambassadors wearing only a towel when attempting to complain about the previous situation to C.C. Another possible running gag is her relationship with Lelouch as they are set up in scenes where they almost kiss but always get interrupted,
 * Kallen Kōzuki has quite the number of similarities with Domon Kasshu from the Sunrise anime Mobile Fighter G Gundam, such as hairstyle, personality, penchant for skintight piloting wear, their respective mecha having the same finishing moves, to the point where fans often joke about Domon being her real Japanese father due to the fact his love interest, ‎Rain Mikamura, has the same seiyuu as Kallen's mother (Yuri Amano).


 * Aki Izayoi from Yu-Gi-Oh! 5D's bears a striking resemblance to Kallen; both sport a crimson theme as well as a similar hairstyle. Personality-wise they are not exact, but similar since they try to isolate themselves from the present society during the story and are hostile to the people they perceive as enemies. They also have possible romantic feelings for the main protagonists of their respective series.
 * In Spice and Wolf, Holo, the main heroine of the series, was voiced by Ami Koshimizu who also voiced Kallen Kozuki. The main lead of this anime, Kraft Lawrence, was voiced by Jun Fukuyama who also voiced Lelouch Lamperouge/Lelouch vi Britannia/Zero.
 * It is notable that the anime was created after both actors, Jun Fukuyama and Ami Koshimizu, won the 1st Seiyu Awards for their respective roles in Code Geass - Lelouch of the Rebellion.
 * In SWRX during a DLC mission, after the Zero Requiem was over, she admits that she felt left out, and knowing that so many people knew about the plan, she felt that they didn’t believe in her. She even went as far as to tell Suzaku that they better not do it to her again.

Quotes

 * "Until I met you, I was only merely plastered with thorns. I wanted to change this truth. I seemingly and recklessly acted. But then, I didn’t believe that anything would come out of it. When my brother was gone, I heard the sound of the heavy doors closing behind me. I cannot allow it. I will fight to the bitter end. I decided that I would not go back. Then, someday, I would have died like my brother. Until the very end, Kouzuki Kallen would not abide by an authority. That bit of willpower I was carrying with me, it slipped away from me, and I can feel it faintly. At that moment, I envisioned you as the star at the break of dawn, inviting me. If I would think that this is for you, my body would feel light. Whatever struggles there were, the pain would go away. I would be the first to come rushing to your battlefield, raging like a lioness, crushing your enemies. I would stand being muddied so that I could create a path for you. Looking back, it's mysterious. Even though I should have loathed and rebelled against Britannia's tyranny. Without knowing it, I held personal devotion only for you. Lelouch, that parting kiss, even if it was a lie, if you had said, "I love you," I would even follow you to hell. Did you know that, didn't you? It's not like you. You're good at manipulating people just by your words. Really, it's not like you to be kind. Is that why you told me to 'live on'? I fell in love with you not just because of that kindness." -Character Poem
 * "It's not bad to just have a little fun once in a while"
 * "That's why I hate Britannians!"
 * (To Suzaku)"Then tell me. What was the point of my brother's life? Who gets to decide whether what's right or wrong?"

Gallery
de: Kallen_Kōzuki