Kokoro Toshokan is a small library nestled in a remote mountain, far from any town. Three sisters, Iina, Aruto, and Kokoro, together run the library day by day. Kokoro has just begun her adventures there, wondering whether she will become a full‑fledged librarian and whether the secluded library will ever attract readers. Determined to realize her dreams, she works tirelessly at Kokoro Library, a place where miracles can happen.