The Detective Is Already Dead novel volume 9 is written by Nigozyu with illustrations by Umibouzu.

With the world in peril once again, Kimihiko Kimizuka returns to his role as the Ace Detective's assistant and sets out on a journey to recover the lost memories of humanity. Using the Sacred Relic discovered by the Oracle, he investigates a past global crisis with the Vampire, Scarlet, at the very heart of it. But as Kimihiko delves deeper, harrowing truths once beyond his reach begin to bubble to the surface…