A idealistic young soldier meets a nurse whose bibliophile young patient convinces him to bloom where he is planted as he pays forward his courage to the people with books from a nearby war-damaged library while helping to pick up the pieces. The collective goodwill visited unto him convinces the soldier to construct what is Kokoro Library as the "place where miracles happen" with the nurse as his spouse with whom he spawns three daughters: Iina, Aruto, and Kokoro.

Several years later, Iina and Aruto have refined themselves into the librarians of Kokoro Library with such quality that their baby sister Kokoro wishes to emulate them. A sunny disposition along with a willingness to eschew the stereotypical professional relationship with her customers are among Kokoro's best assets; still, the road to being the consummate librarian is neither straight nor smooth in fair weather. Kokoro Library's seclusion within the mountains away from the city deters all but the most determined and adventurous users—an attribute that has gotten it in hot water on more than one occasion along with the public grant money necessary for its operation. In spite of the odds against her, Kokoro resolves herself for a euphoric epilogue.