"School mystery number 5ー The 4PM bookstacks. In this school's library... ...There's a special storeroom you can only enter at 4pm. The room is full of books with people's names. Each of these books contains a record of that person's life at this school. What they did here, what they're going to do here. Past, present and futureー it's all written in the book...! But... If you do go to the 4PM bookstacks... ...You have to be careful. There are three kinds of books in the bookstacksー white, black, and red. The white ones have records of people who are alive. The black ones are records of people who have died. and those two kinds are okay... ...But the red books...! Those are the ones you should never ever read."

The 4PM Bookstacks is the fifth of the Seven Mysteries. It is the third school mystery to be introduced in the series, making its debut in Volume 3.

The bookstacks have records of every student in Kamome Gakuen, from the past and even in the future. It is said that white books are for living people, and the black ones are for the deceased.

Upon entering the bookstacks, none of the rumored 'red books' can be found. But in the books, the future is marked with a red page. Nene was led by a butterfly to find her own book and read a bit of her future. After reading her future, the book turned red. A large figure that resembled her appears and stuck up to attack her.

The Fifth School Mystery oversees the "Records" aspect of Kamome Academy.