The Mystery of the Library is the third part of Tian Ran Horse Series and the pinnacle of Aoki.

The Mystery of the Library tells the story that on the opening day of the library, the librarian found the body of a college student on the second floor of the library and the book The Last Photo of Man as a murder weapon. The victim left two death messages-a "く" painted on the carpet and "Remote Interpol" next to the body-and a protagonist on the cover was circled. Both death messages are aimed at the librarian for "a long time", but Leland insists that the death message has no meaning. This time, the art knife dyed from the trouser pocket of the corpse has almost portrayed the image of the prisoner. In addition, by investigating the traces of the scene, he got the final answer: the logic at a glance gave the best answer. A clue is fragile, but if all the clues are organically combined, it will become an unshakable answer.