Kallen Stadtfeld (カレン・シュタットフェルト, Karen Shutattoferuto) is a fictional character in the Sunrise anime series Code Geass: Lelouch of the Rebellion.

Because of this she bears no personal attachment to the "Stadtfeld" name, seeing it as a fake identity; in Japanese credits and apocrypha she is exclusively titled as "Kallen Kozuki" as a result.

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 accidentally pulls back a shower curtain in the third episode, Suzaku sees her bathing under a waterfall when they are stranded on Kamine Island, she is forced to dress in an immodest bunny costume at the start of the second season (to plant a tracking device on Lelouch), and she walks in on a meeting between 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.

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.

The trust seems to be mutual, as Lelouch offers to reveal his identity to her when he notices her curiosity; she declines, though she shows signs of jealousy that C.C., whom she had first met in the previous episode, appears to know.

He tries to kiss her, requesting her to comfort him as a woman, 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 shows a great deal of relief knowing that he's feeling better.

During the Black Knights attempted kidnapping of Empress Tianzi, Kallen is captured by Li Xingke in his Shen Hu, having taken her Guren into battle without replacing its energy filler.

During the second battle of Tokyo, Kallen is rescued from captivity and returned to the Guren (complete with a pilot suit brought by Sayoko), which had been radically upgraded by Lloyd Asplund and Cécile Croomy during her imprisonment.

Following Lelouch's declaration that Britannia will join the U.F.N., 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.

leaders hostage, Kallen insists that she'll take Lelouch down personally, as she possesses the only Knightmare capable of fighting Suzaku's Lancelot Albion.

After a fierce battle, Kallen manages to land a decisive blow on the Lancelot; however, this is at the cost of having her Guren completely disabled in the process and losing consciousness.

She still attends Ashford Academy and is one of the members of Rivalz's new Student Council, but has thrown away her frail cover, signified by her going to school with her preferred hairstyle and the Guren's key around her neck.

She keeps several photos of her friends in her room and smiles at the one with Lelouch before eating a piece of French toast, waving goodbye to her mother before hurrying to school.

Knowing that she would do precisely that was the reason Lelouch remained silent, as had they consummated their feelings, she would have found out about the Zero Requiem, subsequently trying to talk him out of it and, if that didn't work, commit suicide, he wanted Kallen to live on.

Four months later, she is present for Lelouch's miracle over the Student Council, where he asks her to never give up on them and thanking her for staying in school; when he departs, she grimaces over the fact she will never stop loving him.

She is nimble enough to swat a bee with a single swipe (and cut it in thirds), and on two occasions she defeats numerous armed men with little trouble.

In the video game spin-off Code Geass: Lost Colors, Kallen was one of the characters Rai meets, along with the other student council members, and greeted him after he wakes up.

There she later suggested to go to different places that would trigger his memory, leading Milly to vote for Kallen as Rai's caretaker, which Shirley and Nina agrees.

They later encountered the real Black Knights defeating both the terrorists and the Britannian army while they were helping the civilians escape, leading Kallen to have them recognize her and let them leave.

[25] Kallen later went to the Black Knight's hideout and meets with Zero to report about what happened in Shinjuku ghetto and revealed to him about Rai and his piloting skills.

[33] In the Black Knights Route, Rai stops Princess Euphemia from following through with Lelouch's accidental Geass command (an alternate version to episode 22–23), which he was shot in the process.

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.

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.

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.

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 resembles a 17-year-old Suzaku, which she thinks she's imagine it.

Kallen makes an appearance in the Another Century's Episode: R video game in her Knightmare Frame, the Guren Mk-II in an alternative event of R2.

[36] After Zero kidnaps Empress Tianzi, Kallen fought against Xingke in his Knightmare Frame, Shen Hu, while defending the Ikaruga flagship from being attacked by a group of Gun Ru's.