In the early design stages of the Neon Genesis Evangelion anime, creator and director Hideaki Anno proposed including a girl similar to Asuka as the protagonist. Character designer Yoshiyuki Sadamoto proved reluctant to accept the idea of a female character in the lead role after Gainax's previous works like Gunbuster and Nadia: The Secret of Blue Water; he said: "A robot should be piloted by a trained person, whether it is a woman or not makes no difference, but I cannot understand why a girl should pilot a robot". He thus asked the director to use a boy in the role of main character, downgrading Asuka to the role of female co-protagonist. He modeled the relationship between her and the male protagonist Shinji Ikari taking inspiration from Nadia and Jean from The Secret of Blue Water. Asuka should have represented "[Shinji's] desire for the female sex", as opposed to Rei Ayanami's "motherhood", and should have been the idol of Neon Genesis Evangelion. Anno also thought of her as Nadia La Arwal from The Secret of Blue Water with a different hairstyle. In the initial project, she was described as "a determined girl" who adapts to the situation in which she finds herself, passionate about video games and "aspires to become like Ryoji Kaji". In the nineteenth episode, she would have had to be seriously injured in her attempt to protect Shinji, who would have thus "proved his worth" trying to save her.
For the character's name, Anno took inspiration from Asuka Saki (砂姫 明日香, Saki Asuka), the protagonist of the manga Super Girl Asuka (超少女明日香, Chō Shōjo Asuka), written by Shinji Wada; for the surname, he merged the names of two ships used in the Second World War, the Japanese World War II aircraft carrier Soryu and the American aircraft carrier Langley. Despite her multi-ethnic origins, the staff made Asuka's skin the same color as that of Rei Ayanami. For the German language terms used in the scenes with Asuka, staff asked for help from an American employee of Gainax, Michael House, who exploited his basic knowledge of the language, acquired in high school, and a Japanese-German dictionary from a local library. According to Anime News Network's May Callum, Gainax did not pay attention to the dialogue's German grammar, believing the series would never be successful enough to be watched by native German speakers. For Asuka's psychology, Anno relied on his personality, as with the other characters in the series. Staff originally inserted her after the first six episodes to lighten the tones of the series. She was presented with an exhilarating personality without foreshadowing her eventual depressing moments in the latter half. Anno said that he didn't intend to go "that far" at first and that he didn't completely grasp the character of Asuka until he made her "Are you stupid?" (あんたバカ?, Anta baka?) catchphrase, with which the character was definitively born.
During the series's first airing, the director began to criticize otaku, Japanese obsessed animation fans, accusing them of being excessively closed and introverted; therefore, he changed the atmosphere of the second half of the series, making the plot darker, violent, and introspective. Asuka's story reflected the changes: although she had been introduced in an essentially positive role, her character became increasingly dramatic and introverted, going against the expectations and the pleasure principle of anime fans. In the twenty-second episode, Anno focused on Asuka's emotional situation, harassed by her first menstrual cycle, but not considering himself capable of exploring such a feminine theme, he condensed everything into a single scene. Miyamura's interpretation was also important. During the production of the last episodes he inserted scenes in which he represented Asuka with simple hand-drawn sketches, remaining satisfied with the result, saying: "After having drawn Asuka with a marker, as soon as Yuko Miyamura gave it her voice, it was more Asuka than ever". Furthermore, the author's original intent was to insert a long live action segment for the film The End of Evangelion (1997) centered on the character. The original segment focused on a normal day of Asuka, who would wake up in an apartment after drinking and spend the night with Tōji Suzuhara, with whom she would embark on a sexual and sentimental relationship. Misato Katsuragi would have been the roommate in the apartment next to her; Rei Ayanami would have been her colleague and her senpai. In the alternate universe of live action, Shinji would never have existed; walking the streets of Tokyo-2, however, Asuka would hear his voice calling her.
Yūko Miyamura voices Asuka's character in all her appearances in the original series, and the later films, spin-offs, video games, and the Rebuild of Evangelion film series. The only exception is an introspective scene from the twenty-second episode, when other female members of the cast replace the character's voice during a metaphysical sequence. She had originally auditioned for the role of Rei, but staff felt her voice was too energetic, so she was offered Asuka instead. According to Miyamura, Asuka's dubbing proved difficult. She said she wished to "erase Evangelion" and forget her experience with it. Towards the end of the first broadcast, Miyamura suffered from bulimia and found herself in a disastrous psychic state, similar to that of Asuka's character. After the release of the movie The End of Evangelion (1997) she said, "I think I had a kamikaze feeling during the voice-over". The voice actress identified herself so much with the character she took a conversation course in German, decided some of the character's lines, and Asuka's details, such as the cloth puppet in the shape of a monkey featured in her childhood flashbacks. One of her ideas was the German sentences Asuka utters in the twenty-second episode of the series in a telephone conversation with her stepmother.
In a scene from the last episode of the animated series, an alternate reality is presented with a completely different story than in the previous installments, where Asuka is a normal middle school student and a childhood friend of Shinji Ikari, the Evangelion units never existed, and Asuka did not experience any childhood trauma regarding her mother Kyōko. A similar version of events can be found in Neon Genesis Evangelion: Angelic Days, and the parody series Petit Eva: Evangelion@School, where she behaves like a sister towards Shinji. In Neon Genesis Evangelion: Campus Apocalypse, Asuka is a foreign exchange student, and uses a whip in battle. She is also present in Neon Genesis Evangelion: Legend of the Piko Piko Middle School Students. The simulation game Neon Genesis Evangelion: Ayanami Raising Project includes an expansion in its PlayStation 2 version that allows the player to take on the role of Asuka's guardian instead of Rei's. She is also available as a romantic option in Neon Genesis Evangelion: Girlfriend of Steel 2nd, Neon Genesis Evangelion 2, Neon Genesis Evangelion: Shinji Ikari Raising Project and its manga adaptation. In Neon Genesis Evangelion: Anima, Asuka is older, more stable and mature, having developed a strong friendship with Shinji and even Rei. Asuka also merges with her Eva unit turning into a hybrid named Crimson A1.
She also appears in the crossover Transformers x Evangelion, in the video games based on the original animated series and media not related to the Evangelion franchise, including Honkai Impact 3rd, Monster Strike, Super Robot Wars, Tales of Zestiria, Puzzle & Dragons, Keri hime sweets, Summons Board, Puyopuyo!! Quest and in an official Shinkansen Henkei Robo Shinkalion cross-over episode. In the Super Robot Wars franchise, she butts heads with Kouji Kabuto, the pilot of Mazinger Z and Mazinkaiser. It is also implied that she developed crushes on famous heroes such as Char Aznable and Amuro Ray, but proves jealous of Shinji, who crushes for Lynn Minmay of the Macross franchise.
Miyamura noted that Asuka was not called tsundere at the time, but agreed to the definition of her having to hide her feelings in 2007. Furthermore, for Japanese philosopher and cultural critic Hiroki Azuma, she is the "symbol of the outside" in the world of Evangelion, taking Shinji away from his comfort zone in the "Nerv family"; in contrast to Rei, who'd play an "imaginary healing" role, Asuka would be an independent person in reality. Critics also noted that Asuka is iconographically and psychologically opposed to Rei. Rei has blue hair and red eyes and is often associated with the Moon, while Asuka has red hair and blue eyes and is presented in the eighth episode, "Asuka Strikes!", silhouetted by the Sun. Rei is also related to white; the writer Claudio Cordella noted how white is associated in Japanese culture with sanctity, light, eternity, while red is the color of sterile sexuality, traditionally chosen by unmarried girls or geisha for their kimono. Japanese psychiatrist Kōji Mizobe linked Asuka's red to menstruation, Rei's white to altruism, attributing Asuka's unstable behavior to a narcissistic or histrionic personality disorder. Writer Dennis Redmond instead noted that Shinji's Eva-01 is purple, halfway between Rei's blue Eva-00 and Asuka's 02, describing Rei as a symbol of an empty and "lyric neonational interiority", while Asuka as a mirror of a pragmatic and "outrageous multinational exteriority". According to the Polygon, the two girls are two shades of the same spectrum of the feminine, neither of which good or bad in themselves, which Shinji must recognize as autonomous individuals by overcoming the Madonna-whore complex, the inability of some men to see women in their individual nuances, perceiving them dichotomously either as angelic beings or maleficent entities. 2b1af7f3a8