"Daitoshokan no Hitsujikai" is a 12-episode anime series adapted from a visual novel by August. The narrative centers around Kyoutarou Kakei, a second-year student at Shiomi Academy, who receives a mysterious email from someone calling themselves the "Shepherd." The Shepherd claims to guide individuals toward happiness, and Kyoutarou becomes curious about their identity and intentions. This curiosity leads him to the Great Library Club, a group of students who manage the school's vast library and investigate various mysteries.

The Great Library Club consists of several key members: Tsugumi Shirasaki, the club president and a diligent, book-loving student; Misono Senri, a reserved and intelligent girl with a talent for research; Nagi Kodachi, a cheerful and energetic first-year student; and Tamamo Sakuraba, a quiet and mysterious girl who often seems detached from others. Together, they work to uncover the identity of the Shepherd while addressing personal issues and challenges faced by the club members and other students at the academy.

As the story progresses, the Shepherd's messages guide the club members toward helping their peers, often involving emotional or social dilemmas. These interactions reveal deeper layers of the characters' personalities and backstories, such as Tsugumi's struggle with her family's expectations, Misono's feelings of isolation, and Nagi's insecurities about her place in the group. Tamamo's enigmatic nature also becomes a focal point, as her connection to the Shepherd is gradually unveiled.

The series blends slice-of-life elements with light mystery and drama, exploring themes of friendship, self-discovery, and the pursuit of happiness. The Shepherd's true identity and motives remain a central mystery, driving the narrative forward as the club members work together to solve it. The anime concludes with a resolution to the Shepherd's storyline, tying together the characters' personal growth and the bonds they have formed through their shared experiences in the Great Library Club.