The Detective Is Already Dead, Vol. 4 (The Detective Is Already Dead (Novel), 4)

Once the assistant to a great detective, Kimihiko Kimizuka took on a challenge Siesta bequeathed to him after her death and arrived at a conclusion that surpassed his wildest expectations. To bring back the great detective the stuff of miracles Kimihiko and Natsunagi fly to London yet again to obtain evidence that can bring down Seed. On the flight there, however, he hears the same words as he did four years ago: Is there a detective on the plane?