Asako Shibasaki is a core member of the Kanto Library Force, stationed at the武藏野第一图书馆 (Musashino First Library). She serves primarily as a library clerk in the Business Department, holding the rank of First Class Librarian, but her true value lies in her secret role as a key operative in the newly formed Intelligence Department. She is also the dormitory roommate and close friend of her enlistment comrade, Iku Kasahara.

In appearance, Asako is a petite woman with long, straight black hair and dark eyes, standing 157 cm tall. She is notably beautiful and socially adept, which makes her popular, especially among men. However, this attractiveness often breeds jealousy among other women, an experience she has been familiar with since her student days. Beneath her charming exterior lies a sharp, sarcastic, and exceptionally intelligent individual. Her tongue can be quite biting, and she is known for teasing her friends, particularly Iku and Hikaru Tezuka.

Asako possesses superb intelligence, resourcefulness, and situational judgment. She has a talent for rapidly gathering information and managing interpersonal relationships, which led to her recruitment into the intelligence division. Her role often requires her to use her wits and even her appearance strategically to obtain information, a tool she is not afraid to employ. This calculated nature is a defense mechanism developed from past social wounds. During high school, her blunt honesty and refusal to hide her true feelings led to her being ostracized by her peers. As a result, she learned to wear a social mask, hiding her genuine emotions to navigate social situations and protect herself from further hurt. This created a deep-seated reluctance to trust others fully.

Her relationship with Iku Kasahara is transformative. Despite her initial vow to never trust anyone, Iku’s straightforward and earnest personality gradually breaks down Asako’s emotional barriers. Iku becomes the one person Asako truly considers a close friend, a connection she deeply values. Their friendship is a cornerstone of her personal development, allowing her to show a more vulnerable side.

Asako’s romantic life is complex. She initially develops an attraction to Atsushi Dojo, fascinated by him precisely because he seems immune to her charms and would likely never fall for her. Knowing her friend Iku harbors feelings for Dojo, Asako makes a confession that is framed as a joke, effectively removing herself from contention while observing the situation from a distance. Her genuine romantic relationship eventually develops with Hikaru Tezuka, a younger but highly capable member of the Library Force. They share mutual respect for each other's competence, and Tezuka had previously helped her by pretending to be her boyfriend to ward off persistent suitors. Their relationship comes to a head when Asako is kidnapped by a jealous stalker. The culprit is a fellow librarian harboring unrequited feelings for Tezuka, who colludes with a man obsessed with Asako. After Tezuka successfully rescues her, he confesses his feelings, and Asako, shaken but accepting, asks him to cherish her, solidifying their romantic bond.

Among her notable abilities, Asako excels in intelligence work. She is adept at quickly processing information, analyzing situations, and managing human relations to achieve her goals. Her role often involves supporting the Defense Division during emergencies, providing critical information and tactical support. While not a frontline combatant like the Library Special Forces, her strategic mind and information-gathering skills are indispensable assets to the Library Force. Her personal journey sees her evolve from a guarded, cynical individual who uses her beauty and wit to keep others at a distance to someone who learns to trust and form a genuine, lasting partnership.