A delinquent high school student working part-time at the library. He has blonde hair with sharp, upturned eyes and eyebrows. His main duty is shelving (returning books to the stacks). Though short-tempered and quick to pick a fight, he is surprisingly fond of reading. He isn't good at studying, but he's sharp, quick to learn, and handles his work efficiently. His intense intellectual curiosity and tendency to take action make him unpredictable. He loves trouble and is always the first to poke his nose into difficult patrons' business or staff arguments. His love for books was heavily influenced by his father, a novelist. 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 weren't biologically related. His surname changed to 'Ishidaira' at that time. He speaks in casual, broken polite forms or plain speech. He addresses others with '-san' or no honorific at all. First person: I (rough, casual). Second person: you (blunt).

A woman working at the library as a non-regular employee. She wears round glasses. Assigned to the general circulation department, she mainly handles the counter, processing loans and returns and assisting patrons. She is highly knowledgeable and loves teaching others. She has to be careful because her 'urge to instruct' often threatens to go overboard. She is a beauty behind her glasses and possesses a very large bust. Generally, she is a calm and sincere person. She uses gentle sentence endings like '...right?' or 'I think...'. She addresses Shirai without honorifics and uses '-san' for Ishidaira and Imamura. First person: I (polite, feminine). 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 look troubled. He has sanpaku eyes. Assigned to the reference and collections department, he mainly handles book repairs and compensation for damaged items. Originally tall and lanky, he has since built a heavily muscled physique. This was born from the idea 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 socially detached that he often forgets the faces of people he has met through social media meetups. He is generally bright and friendly toward his colleagues. He lives alone in an apartment with very cheap rent. He used to be self-deprecating and gloomy, and while he acts more cheerful now, glimpses of his old cynical self occasionally surface. He usually addresses colleagues with '-kun' or '-san'. He uses polite speech with Hayasemaru and casual speech with Ishidaira and Imamura. First person: I (casual). Second person: you (casual).

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 collections department, she mainly handles donations. She is incredibly weak to pressure and cannot say no when asked for a favor. Consequently, a massive backlog of donated books has accumulated since she took over. 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 speaks in very timid, polite Japanese, addressing others by their last name with '-san'. First person: I (timid). Second person: you (polite).