A cold and aloof character in the manga, her personality was drastically changed in the anime adaptation[2] at the behest of Kunihiko Ikuhara, where she became stubborn.

In the manga, she is portrayed as imperial, ancient, conservative, old-fashioned, traditional, serious, disciplined, and practical, having contempt for men and disliking modern romantic relationships.

Though these arguments are usually petty, early in the series Rei attempts to usurp Usagi as the leader of Sailor Guardians.

Even though Rei does become more loyal to Usagi, with slightly calmer emotions in the later seasons, she still remains somewhat more of a typical teenager than her manga counterpart.

In the anime, Rei also tends to engage in long periods of antagonizing Usagi (who returns the same reaction), as a running gag in their arguments.

The one exception is in a manga side-story centering on her, Casablanca Memories, which tells of Rei's friendship with her father's young secretary, Kaidou.

She is shocked when he suddenly announces his engagement to another girl and his decision to become a politician, despite having once said that he did not like what had happened to Rei's family as a result of her father's work.

In the manga, this is the only potential romance in her life; in the live-action series, nothing of the sort is ever shown, as Rei unquestionably detests boys.

[5] In the anime only, she "dates" Mamoru Chiba in the first season (though he thinks they are just friends), and occasionally seems open to a relationship with Yūichirō Kumada, her grandfather's pupil.

Later on, members of the Dead Moon Circus harass Rei with a reflection of her young self, which mocks her for her friendships and her dream of being a priestess.

Rei is able to defeat this illusion, and in the process gains her Sailor Crystal along with the memory that, long ago, she had in fact made a vow of chastity to Princess Serenity.

Rei's lifelong dream is to become the head priestess at Hikawa Shrine, and much of her life is influenced by spirituality, particularly in the manga.

As a character with different incarnations, special powers, transformations and a long lifetime virtually spanned between the Silver Millennium era and the 30th century, Rei gains multiple aspects and aliases as the series progresses.

In Japanese, the name for the planet Mars is Kasei (火星), the first kanji meaning 'fire' and the second indicating a celestial object.

[18] Most are offensive attacks, although as a priestess, she also possesses a certain amount of psychic ability, and is able to do fire-readings, sense danger, and subdue evil spirits.

As she grows stronger, Sailor Mars gains additional powers, and at key points her uniform changes to reflect this.

The first change takes place in Act 41 of the manga, when she obtains the Mars Crystal and her outfit becomes similar to that of Super Sailor Moon.

As Princess Mars, she lived in Phobos-Deimos Castle and wore a red gown—she appears in this form in the original manga, as well as in supplementary art.

Phobos and Deimos reveal their true forms when delivering the Mars Crystal to her and refer to her using her princess title.

In addition to some psychic talent, including occasional unprompted premonitions,[28] Rei is able to do fire readings and to dispel evil spirits.

She does the latter by performing Kuji-Goshin-Ho, a ritual which consists of chanting nine words of power (Rin, Pyou, Tou, Sha, Kai, Jin, Retsu, Zai, Zen!)

[36] Her first attack to be the same across all versions is "Burning Mandala," which incorporates Buddhist symbolism in the fiery rings Sailor Mars summons.

The latter is associated with her skill as an archer, and although she does not receive a physical bow, she recalls some advice given to her by Michiru Kaioh—"[If] you think you're being taken advantage of by the enemies, stretch a line taut in your soul.

[46] In an intermediate design, the pendant that sat at her waist in the early manga was also intended to be worn as a necklace in her civilian form.

Her given name is in katakana rei (レイ); possible meanings include "spirit" (霊), "companion" (儷), "cool" (冷), and "zero" (零).

Because katakana is the alphabet usually used for foreign loanwords, it may also be intended as a Western name, such as Raye (which is indeed used in American continent localizations) or Rae.

[48] It has been noted that her outfit as Sailor Mars echoes the colors of her miko robes, and she is the only character that is mostly tied into tradition.

[49] In the Japanese anime television series, Rei is voiced by Michie Tomizawa, who later said that working on Sailor Moon had been "exactly like magic" for her.

In the Viz Media English adaptation produced in association with Studiopolis, her voice is supplied by Cristina Vee, a long-time Sailor Moon fan.

[53][54] In the musical productions, Rei has been portrayed by nineteen actresses: Hiroko Nakayama, Misako Kotani, Asuka Umemiya, Hiromi Sakai, Eri Kanda, Megumi Yoshida, Aiko Kawasaki, Risa Honma, Kanon Nanaki,[55] Karen Kobayashi.,[56] Kazumi Takayama, Ranze Terada, Kotomi Hirai, Kyoko Ninomiya, Yui Hasegawa, Seira Hayakawa, Rei Kobayashi, Hina Okamoto, and Miku Ichinose.