The Detective Is Already Dead Novel Volume 9 is written by Nigozyu with illustrations by Umibouzu.

With the world in peril once again, I, Kimihiko Kimizuka, returned to my role as the Ace Detective's assistant and set out on a journey to recover the lost memories of humanity. Following a trail of leads and using the Sacred Relic discovered by the Oracle, we sought to investigate a crisis from a certain world in the past, and the Vampire Scarlet was at the center of it. But the deeper we delved, even the harrowing truths that were once beyond our reach began to bubble to the surface. This is the story of detectives who continued to pursue the mysteries that remain hidden from the world—and the story of a Vampire King who defied the injustices of the world and fought ’til the very end.