Kiichi Ishidaira is a high school delinquent whose path takes an unexpected turn when he visits a public library for the first time in a decade. Upon arriving, he is confronted by librarians Sayaka Hayasemaru and Satoyuki Shirai, who inform him that he never returned a book he borrowed ten years earlier. Unable to pay the replacement cost, Ishidaira begins working at the library as a part-time employee, a decision that introduces him to an unfamiliar world of organization, community service, and the quiet dignity of public institutions.

The story unfolds primarily within the walls of a Japanese public library, a setting that serves as both a workplace and a stage for a variety of small but significant dramas. Ishidaira, whose belligerent exterior conceals a natural inquisitiveness, slowly rediscovers a love for learning and books under the guidance of his senior coworkers. Hayasemaru is a passionate librarian who acts as his mentor, using the incident of the lost book to steer him toward a more constructive path. Shirai, initially physically weak, has notably bulked up to better handle uncooperative patrons and threats to his colleagues, and he often uses his assertiveness to maintain order.

The narrative is driven by the everyday problems that arise in a community library, such as damaged books, noise complaints, and the mysterious circumstances surrounding certain returns. Alongside his coworkers, Ishidaira works to solve these issues, each case revealing more about the patrons who use the library and the value of the space itself. The series is a workplace comedy that focuses on the reformed delinquent’s adjustment to a structured job and the quirky, dedicated team around him, transforming a mundane public service setting into a backdrop for character growth and small, human-centered mysteries.