Clamp's head writer Nanase Ohkawa originally created Kamui during high school as character in a story involving warriors fighting for justice.

His incorporation to X includes themes Ohkawa thought about since she was a student, such a possibility of an evil alter ego and whether mankind is more important than the Earth.

Their first illustration of Kamui gave them a feeling of Ashura, a character from RG Veda based on his appearance in Tokyo's destroyed area.

Ohkawa also applied to Kamui and Fūma ideas she had as a child, such as a dual nature, because she states people can be considered good or evil.

[8][9][10] Because Kamui did not have many lines in the original video animation, Suzumura lacked a full impression of him before more of his character was explored in the television series.

[16] Despite his mannerism, Kamui reveals his personality is a facade when Hinoto shows him the future death of Kotori as well as his relation with the end of the world which heavily angers him.

[19] Following the death of his aunt, Kamui shows his true resolve in regards to the apocalypse; He is not interested in society or the planet's pollution but instead wants to protect his two childhood friends.

[20] Kotori's death causes a major impact into Kamui, but manages to recover thanks to one of the Dragons of Heaven, Subaru Sumeragi, who would become his mentor in the narrative.

[21] From this point on, Kamui becomes more concerned about his role in the Armageddon due to the lives his enemies might take in the process but is powerless against the sadistic Fuma.

[24] Contrary to the kindheartedness with which his childhood friends Fūma and Kotori Monou remember him, Kamui appears distanced and cold, and avoids interacting with them.

[33] For the next month, Kamui starts living with the Dragons of Heaven Sorata Arisugawa, Arashi Kishū and Yuzuriha Nekoi, which helps him form new friendships while often meeting Subaru.

[37] While the manga's serialization was put in hiatus, leaving the story unconcluded, its animated adaptations show Kamui reaching different fates.

In the final battle, Kamui sacrifices his life to create a barrier that will protect mankind and passes Fūma his will, which restores his personality.

[39] An alternative version of Kamui appears as one of the vampire twins Seishirō is seeking in Clamp's crossover series Tsubasa: Reservoir Chronicle.

[43] Outside manga and anime, Kamui also appears as a playable character in two video games based on the series; X: Unmei no Sentaku.

[46] Mike Crandol from Anime News Network found Kamui not less interesting than other supporting characters due to his attitudes.

Matthew Warner from The Fandom Post states that while Kamui's antiheroic portrayal makes him look like a "prick", he becomes more appealing the move his backstory is displayed.

[49] Chris Beveridge from Mania Entertainment noted that Kamui's tragic backstory explored in the series "adds a new dimension" to the character.

[50] Zac Bertschy from Anime News Network noted that Kamui managed to develop himself despite retaining his brooding and distanced persona.

[52][53] On the other hand, Andy Hanley from UK Anime Network found that despite the appealing backstory of Kamui to understand his emotions, it still "doesn't make him any less enjoyable to watch" when compared to other characters.

[54] For the film, Bamboo Dong from Anime News Network praised Tomokazu Seki role voicing Kamui due to how he displays the character's emotions.

[10] In promoting the anime Karakuri Circus, producer Masao Maruyama also praised Seki's work as Kamui alongside Kōhei Kiyasu's from Hajime no Ippo for presenting a natural progression in their characters.

In the book Understanding Manga and Anime writer Robin E. Brenner stated Clamp had none of those intentions, and compared them with the more explicit relationship between Subaru and Seishirō.

[68] Sakura Eries of Mania Entertainment said despite his strength, Kamui was easily defeated by Syaoran, who continuously fights different enemies in the same arc regardless of wounds.