KALLEN STADTFELD / KAREN KOZUKI
Age: 17/18 (in the second season)
Date of birth: 5 May 2000 a.t.B.
Zodiacal Sign: Taurus
Height: 1.60 cm
Nicknames: Red Lotus,
Ace of the Elevens/Black Knights,
Seiyuu: Ami Koshimizu
Kallen is a Britannian-Eleven girl, who believes herself to be a Japanese person at heart and prefers to be known by her birth name. Her father is Britannian and her mother is an Eleven; her father comes from a prestigious Britannian family, which Kallen benefits from. She attends the Ashford Academy, where she is a member of its student council and is one of its most outstanding students. Her brother, Naoto Kōzuki (紅月ナオト, Kōzuki Naoto) , with whom she had a deep connection, was a former leader of the resistance organization before his death.
Both Kallen's stepmother, a Britannian, and biological mother live with her in the same house, but her biological mother is employed as a maid and is often mistreated by both her stepmother and Kallen herself. After her biological mother is arrrested for using Refrain (a fictional drug which lets people think they're reliving the past), Kallen changes her views and decides to fight against the Britannian Empire not only for her brother, but to fulfill her new wish for a world in which she can live happily with her biological mother.
This aspect of her character contrasts the frail-girl image she uses as a public front.
Kallen leads a double life as a normal Britannian student and as a member of a guerrilla resistance group against Britannia, which is later reformed into the Order of the Black Knights by Lelouch Lamperouge. When she is in school, Kallen portrays herself as a weak-bodied high school student who obeys all of the formalities. However, her personality changes in to a very strong-willed and forceful one when she acts as a resistance fighter.
As a running gag, Kallen ends up nude 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 in an immodest bunny costume 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 intending to complain about the previous situation to C.C.
In an interview reported by the anime magazine Newtype USA, seiyu Ami Koshimizu talked about the difficulty of voicing Kallen because of the double life that her character leads. 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.
Kallen appears early in the first episode, driving a truck with C.C.'s capsule. 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 mechs. She sacrifices her mech to allow Lelouch to escape, despite not knowing who he really is.
After this incident, Lelouch's unfamiliarity with his Geass causes him to reveal knowledge of the Shinjuku incident to Kallen, leading her to suspect him of being their unknown benefactor. Lelouch tricks her by playing a recorded message of himself on the telephone, drawing her suspicions off him by pretending to be the mysterious Zero . With the formation of the Black Knights and Zero's increasing number of victories over the Britannian forces, Kallen comes to greatly admire him, evident in her ecstatic reaction to her appointment as head of his personal guard. She even tries to assassinate Suzaku Kururugi after learning that he is the pilot of the Lancelot, believing it would benefit Zero's goal.
Once the Black Knights begin receiving new Knightmares, Zero gives Kallen the newly developed Guren Mk-II. With its powerful radiation-emitting arm and speed matching that of Suzaku's Lancelot, Kallen becomes one of the Black Knights' most talented pilots, often facing off against Suzaku and usually proving an even match for him.
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 Lelouch abandons the battle to rescue his sister, Kallen follows him. She witnesses his confrontation with Suzaku and learns about his true identity and his Geass power. She flees in shock rather than help Lelouch deal with Suzaku.
One year later, Kallen is still part of the Black Knights. Along with C.C., she is the only member who knows Lelouch's identity and secret power. After C.C. awakens Lelouch's suppressed memories, Kallen confronts him, wanting to know if her faith in Zero is motivated by her own beliefs or a result of Lelouch's Geass manipulating her. Lelouch insists that her loyalty is her own decision. She seems to accept this, and still supports Zero, even though she prefers to see Lelouch and Zero as separate entities. She also desires to be in his inner circle as C.C. is, so that she won't be left in the dark about his plans; though she won't admit it, C.C. easily sees through the act and playfully teases her about it.
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 Gilbert G.P. 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 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 once their mission is finished, but is interrupted by C.C. before he can explain why.
During the Black Knights attempted kidnapping of Empress Tianzi, Kallen is captured by Li Xingke in his Shenhu, having taken her Guren into battle without replacing its energy filler. Lelouch swears that he'll rescue her, though Diethard Reid suggests abandoning her as a casualty of war. 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 a prison in Area 11, and subsequently transferred into a more comfortable solitary cell by Nunnally, who also gives her a dress to wear. The two strike up a rapport about Lelouch. Suzaku approaches her after Shirley's death, intending to use the Refrain drug 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.
Kallen is a skilled Knightmare Frame pilot, rivaling the abilities of even the Knights of Rounds. She is acknowledged as the best 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; she also has the highest possible "Loyalty" score of 100. With 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; the upgraded arm of her Guren Flight-Enabled Version can also attack from long range. 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. Outside of a Knightmare, Kallen displays superior fighting abilities, is highly resourceful, and she is apparently intelligent since her grades in school are top of the class.