Seira Kamui holds the position of student council vice-president at St. Maris Academy, an institution dedicated to training demon fighters. Her heritage includes partial European descent (one-quarter), contributing to her portrayal as foreign fanservice. She has blonde hair styled in waist-length twin tails, blue eyes, and pale skin, featuring a large bust consistent with the series' emphasis on voluptuous female characters.

Her standard academy uniform is modified to include a cupless corset, garter belt stockings, a cross necklace, and a collar. In combat against supernatural threats, she wields twin pistols in a guns akimbo style, embodying the "Thief" role within the council's Fighter-Mage-Thief dynamic. Her combat skills showcase improbable accuracy, enabling her to fire shots forming cross patterns.

Official media depicts her capture alongside fellow council members Hikaru Izumi and Yuki Ayatsuji by the demon Barmus. This leads to a forced disrobing scene before brainwashed peers during a school assembly. Subsequently restrained, she is forced to witness Hikaru's rape and torture by Barmus. Demons specifically target her posterior for assault, reflecting a recurring motif of sexual violence directed at her physical traits.

Her background includes an attraction to Hikaru's younger brother Shou in the original game narrative, displaying tsundere tendencies due to romantic inexperience; this subplot was omitted from the anime adaptation. The conclusion of the anime OVA implies her eventual fate involves sexual enslavement and forced impregnation by demons, aligning with Barmus's objective to use the student council as breeders for demon offspring.