Mai is depicted with short Red/Orange hair and a rather large bust. She is typically cast as a sisterly friend of Mikoto, the guardian of her brother Takumi Tokiha, a close friend to Natsuki Kuga but usually at odds with her, and a potential love interest of Yuuichi Tate and Reito Kanzaki. She is associated with fire, and in all series wields 4 large golden rings with magatama as weapons. She also uses a mitsu tomoe as her symbol. She has a fear of spiders in both anime and manga. Running gags include Mikoto burying her face in Mai's chest or Mikoto otherwise being possessive of her, Mai's bust size, and her cooking abilities.
In the anime, Mai's elements are a set of 4 golden rings around her wrists and ankles. The rings allow her to use fire-based attacks and the power of flight. Mai also is capable of creating barriers around herself to block attacks. Mai's HiME mark is located on her right breast, which is said to be controlled by Cancer, her Zodiac sign.
Her Child is Kagutsuchi, a dragon-like creature capable of spitting destructive fiery balls and named after a Japanese god of the same name. It also is capable of melee fighting, and has a jet mode which allows it to travel at high speeds. The sword in its head, the Sword of Sealing, made by the Obsidian Lord, acts as a seal on its powers, allowing the Obsidian Lord to suppress it when needed. During the final battle, the HiME's attack on the HiME star weakens the Obsidian Lord and destroys the sword, loosening the control and allows Kagutsuchi full access to all its power to destroy the Obsidian Lord within Reito.
In the beginning of the series, Kagutsuchi appears to be by far the strongest Child among other HiME's childs. Toward the end of the series, when stronger Childs appear (e.g. Shizuru's Kiyohime and Mikoto's real Miroku), Kagutsuchi's power is challenged. However, when its seal is finally removed, it is doubtful that there is any Child that can come close to its power. Interestingly, Kagustuchi is also the only child shown to actually resist death; once, when Alyssa attacked Mai and her friends with Artemis' Golden Lightning, Mai sacrificed herself by flying herself and Kagutsuchi into the path of the lightning, protecting everyone while incinerating herself and Kagutsuchi. However, Kagutsuchi merely reformed into its jet form, Mai regenerating on top of its head and, without Mai's command or consent, flew into space, dodging all of Atremis' subsequent attacks and destroying the other child. Though Mai seemingly died (again) in the explosion, she was shown alive and well the very next day..
In the manga, she starts off with her trademark rings already as a HiME and is fairly skilled at fighting. Her Key is Yuuichi Tate, and her Child is Kagutsuchi.
When she becomes a QUEEN, she becomes even more powerful and is able to summon a darker Kagutsuchi without the use of a Key. She gains two larger rings of fire floating behind her back, in addition to her standard 4 rings.
In the final battle, Kagutsuchi draws itself into the sword stuck in its head, creating the Sword of Kagutsuchi which Mai, Yuuichi and Natsuki wield to bring down the HiME STAR CHILD that had absorbed her brother. However, unlike in the anime, Kaguthuchi remains after the HiME star is destroyed, as the CHILD is the product of the HiME and the Key rather than on the HiME Star itself, and is no-longer in it's sword form.