The Case Records of the Biblia Secondhand Bookstore Spin-Off Koguchi-san and My Biblia Fight Club Activity Diary

is a Japanese light novel series written by Minato Ishikawa, with illustrations by Okada Amitsu and supervision by the creator of the original light novel series, En Mikami. The series began publication on October 10, 2018 by ASCII Media Works under their Dengeki Bunko publishing imprint. The original light novel series was published by ASCII Media Works under their Media Works Bunko imprint.

Synopsis
Kyohei Maekawa, who was secretly reading a novel to his friends at a high school in Kamakura. He also wrote a novel full of Chuunibyo, but one day he lost the notebook that wrote the novel at school.

I picked up Koguchi Ushirono, a member of the library. He was a small animal, a reading girl who entered the world of works when he was absorbed in reading. The old library is the only place where you can read with peace of mind for Koguchi, who cannot read in a crowded place because he is too enthusiastic. However, the old library, which has few users, is in danger of being abolished, and the two decide to challenge the original rule book review battle "Vibria Fight" to protect the old library.

In Vibria Fight, which presents recommended books, we introduce many real masterpieces. A page of youth of high school students who like books, in which Mr. Shiori of the original novel also appears.