A delinquent high school student working part-time at the library. He has blonde hair, upturned eyes, and sharp eyebrows. His main duty is shelving (returning books to the stacks). While short-tempered and quick to pick a fight, he is surprisingly a book lover. He struggles with schoolwork but is far from stupid; he learns quickly and handles his job efficiently. Driven by intense intellectual curiosity and a proactive nature, his actions are often unpredictable. He loves drama and tries to stick his nose into trouble caused by patrons or arguments between staff. His love for reading was heavily influenced by his novelist father. However, his parents divorced when he was in second grade, and he was raised by his mother. He admired his father but was shocked to learn from his mother that they are not biologically related. His surname changed to "Ishidaira" at that time. He speaks in casual, broken polite forms or plain informal speech. He addresses others with "-san" or no honorific. First person: I (rough, casual). Second person: you (blunt) / you (rough).

A woman working at the library as a non-regular employee. She wears round glasses. Assigned to the general circulation department, she primarily handles patron services at the counter, such as checking books in and out. She is highly knowledgeable and loves teaching others. She has to be careful because her "urge to explain" often threatens to spiral out of control. She is a beautiful woman behind her glasses and possesses a very large bust. Generally, she is a gentle and sincere person. She speaks with a soft, guiding tone, often using phrases like "right?" or "I think so." She calls Shirai by his last name and addresses Ishidaira and Imamura with "-san." First person: I (polite). Second person: you (polite).

A man working at the library as a non-regular employee. He wears square glasses. He has sharp eyes, a snaggletooth, and even when smiling, his eyebrows tend to look troubled. He has sanpaku eyes. Assigned to the collection management department, he is primarily responsible for book repairs and handling compensation for damaged books. He has a heavily muscled, ripped physique. This is the result of training under the logic that "if I look strong, patrons won't mess with me, and I can protect the peace of the library." He loves books but hates people. He especially despises those who don't take care of books. He is so bad with faces that he forgets people he has met in person from social media. He is generally bright and friendly toward his colleagues. He lives alone in an apartment with a monthly rent of 18,000 yen. He used to be self-deprecating and gloomy, and while he acts more cheerful now, glimpses of his old cynical self occasionally surface. He generally addresses colleagues with "-kun" or "-san." He uses polite speech with Hayasemaru and informal speech with Ishidaira and Imamura. First person: I (casual). Second person: you (soft).

A woman working at the library as a non-regular employee. She has drooping eyes and eyebrows, and wears her hair in a half-up bun. Assigned to the collection management department, she is primarily in charge of donations. She is extremely weak to pressure and cannot say no when asked for a favor. As a result, donated books have been piling up since she took the position. Her left bangs are long, covering one eye. She often looks overwhelmed, to the point where it seems like her soul is escaping through her mouth. She lives with her parents. She generally uses polite speech, addressing others by their surname with "-san." She is very timid. First person: I (polite, timid). Second person: you (polite).