The end of the 19th century—a vampire's wife is murdered, and the detective known as the "cage user" is called in to solve the crime. But there's more to the detective and the curtained birdcage he carries...after all, when solving a case involving a monster, it might just take one to know one!

Demons..." Not a single one of hell's messengers possesses a life that cannot be stolen away. Not even the immortal "vampire," nor the lifeless "undead." The murder of the vampire bride will finally be solved! After that, the stage will shift to a magical city, teeming with phantom thieves and mysterious folk... London!

1889, the magic city of London. The Iron Man Phileas Fogg has received a warning letter from the phantom thief Lupin. What is Lupin after? A black diamond in Fogg's ownership with a most peculiar history, "The Penultimate Night." The preeminent forces of Sherlock Holmes, Scotland Yard, and the detectives specializing in demonic cases have been assembled to put a stop to Lupin's plan. In this struggle for the diamond, who will have the last laugh?!