The story begins with the eldest sister Iina appraising the red library uniform designated for her baby sister Kokoro who is starting out as a librarian at Kokoro Library. After the middle sister Aruto scolds Kokoro to always be punctual and Iina photographs the occasion, Iina and Aruto's divergent perspective of professional conduct gives way to the three sisters opening the library only to encounter little action until the lunch break where Kokoro is advised to be patient -- very sage counsel when her first customer Kaede Hoshino arrives searching for an out-of-print book that Kokoro successfully locates on her own. After a calendar week, Kokoro ironically finds that Kaede Hoshino's failure to return the borrowed book in person causes her hefty heartache that leads to a collaborative hitchhiking sequence that proves Kokoro's ability to travel safely by herself but is otherwise in vain; during the drive home, Iina and Aruto exchanging notes about having to be strict becomes the preamble for Kokoro having forgotten that she only had to check the mail at home before undertaking the journey she did.