Ireia Kitty is a first-grade Armed Librarian of the Bantorra Library, ranked among its five most powerful members. In her fifties, she focuses on instructing trainees and avoids frontline combat unless emergencies demand it. Her kind, rational, and motherly nature fosters deep trust and affection from colleagues, making her a stabilizing influence on the younger, often impulsive Librarians. She maintains a calm demeanor, prioritizing thoughtful consideration over haste.

Visually, she appears as an elderly woman with grey hair pulled into two tight buns behind her ears, wearing spectacles and a dark blue dress featuring a red ribbon at the throat. She consistently wears an apron tied in a large bow at the back and white gloves. Her younger self presented a stark contrast: long blonde hair and flamboyant attire, including a low-cut red ballgown-style dress, a feminine lace choker, and metal or stone gauntlets.

Her combat style emphasizes immense physical strength for hand-to-hand engagements, allowing her to effortlessly lift or throw heavy objects like boulders or steel beams. Despite her age, she possesses remarkable agility, capable of leaping significant distances. Her supernatural ability grants localized time control over objects or individuals within her direct line of sight, enabling her to accelerate, decelerate, or completely halt time. She can also render herself temporarily invulnerable by stopping time for her own body, though this immobilizes her and blocks telepathic communication. Using these powers consumes substantial energy, rapidly depleting her stamina and limiting their duration and scope.

Her past was notably more perilous and volatile compared to her later role as a mentor. Her life ends during a conflict with Meats—explosive entities infected with Cerulean Death and driven by hatred for the Armed Librarians—when a horde overwhelms and kills her.