On the corner of a modern town, on higher ground atop a hill is a Western building, old as though it were left behind by time. Closed for many years, it is a private library called "Clover Library". Loving books from a young age, Aikawa Chihiro wishes to one day have a job involving books. She then earns the job of a live-in custodian of the Clover Library.
With a look like that of on old photograph, strange and impossible things occur there, one after another.
The sense of being gazed upon, even though nobody should be inside. Books that moved before one knew it. Large, large shadows peering through the window. Finally, at night, people that come out of nowhere who call themselves "frequenters since the olden days".
Surrounded by these individuals- all of whom possess distinct personalities- Chihiro prepares the library for its opening day. Eventually, she's no longer able to suppress her suspicions and confusion over the continuous occurrences of strange happenings, as well as the truth behind who or what these frequenters really are.
Struck by her questions, this is their reply:
"I'm sorry. We kept our mouths shut about it. We are not human." "In truth, we are actually books."
[Translation of the official website's story summary.]