Shinya 0-ji no Shisho Minarai

Overview

High school student Ann Mihara is staying with her host family over the summer at a private library on the outskirts of Sapporo, commonly known as the "Library Mansion." Breaking the rules told to her by the unsociable owner, Sage, Ann ends up getting lost in the library in the middle of the night. There she finds herself in a dilapidated underworld - the Library Labyrinth where "phantoms of stories" wander! Ann, who has been appointed librarian of the labyrinth, is ordered to "have as many people as possible read the library's books and restore the labyrinth"...!? In an old mansion surrounded by beautiful nature, the story of an unsure girl begins to take shape. (Source: Kadokawa, translated)

Source: AniList