Reika Kitami began as a transfer student ensnared by the Rose Cross witchcraft club. Lured to an abandoned warehouse under false pretenses, she was restrained and raped by club members, who preserved her virginity for a ritual sacrifice. During the subsequent ceremony in the school basement, club leader Nami Kozono stabbed her with a sword, but the ritual failed. Mortally wounded, Kitami struck a pact with the Devil to survive, gaining supernatural abilities in exchange for her soul—a bargain that twisted her mind toward evil.

Twelve years later, she worked as a nurse at the same academy. Knowing her demonic contract neared expiration—which would bring death and damnation—she scoured ancient texts and organizations like the Priory of Sion for escape methods. She discovered soul-succession, a ritual requiring a virgin host body performed on Walpurgis Night to transfer her soul and evade the Devil. During this time, she cultivated a romantic relationship with student Naoto Yamanishi at another school before transferring back to the academy.

There, she targeted virgin students, utilizing her demonically granted ability to grow male genitalia to sexually assess candidates like Mika Ito and Miyuki Nonogusa. She focused on Kurumi Imari after student council president Rika Shiraki lost her virginity due to a love spell. Kitami manipulated student Taki Minase, seducing him and embedding a lesser demon within him to ensure loyalty. She forcibly recruited occult club leader Kaori Saeki and her followers through repeated rape and magical coercion. She also tortured former Rose Cross member Hiroko Takashiro for information about her past sacrifice.

Kitami kidnapped Imari, administered aphrodisiacs, and restrained her with a chastity belt. During the Walpurgis Night ritual in the school basement, she initiated the soul transfer into Imari's body. Minase and Takashiro interrupted by reciting a Forbidden Spell, seemingly killing Kitami's original body. Yet, a fragment of her soul successfully transferred into Imari, remaining sealed within her by Takashiro's magic.

Years later, Imari worked as a psychic investigator for the Tokken agency. Kitami's soul surfaced intermittently, briefly controlling Imari's body to burn the Bible Black grimoire before assaulting Saeki. Her soul fully revived when occultist bank robbers, led by Jody Crowley, performed an incantation during a hostage situation. This shattered Takashiro's seal, allowing Kitami to seize permanent control over Imari's body. She then allied with Crowley to pursue new supernatural goals, including recovering mystical artifacts like the Spear of Longinus.

Throughout her existence, Kitami wielded diverse dark magic: empathic arousal induction, biological manipulation (including forced ejaculation causing madness), pyrokinesis, telekinesis, mind control, pain tolerance, protective glyphs, body puppetry, and sensory deprivation fields. Her physical capabilities encompassed twisting an adult's head 180 degrees and lifting humans by their skulls.

Her soul persists within Imari's body, actively pursuing sinister occult objectives without resolution.