Episode 42

A Perfect Murder and Murderer (Part 2) (完璧な殺人と殺人者 (其の一),) is the 42nd episode of Bungo Stray Dogs anime series and the fifth episode of the fourth season. It aired on February 1, 2023.

Summary
Poe scans the manuscript to look for possible clues that may help Ranpo in the baffling case. When asked by his companion, Minoura talks about the Kindaichi murder case, where the titular author was found murdered in his inn room just as depicted in the novel he was writing at the time. Poe reads from the manuscript that the murderer is the victim's acquaintance motivated by anger, similar to Ranpo's deduction, and finds traces of water droplets on the last page. As he inspects the page to be photocopied rather than originally handwritten, he surprisingly receives a phone call.

During their ride, Mushitaro finds Ranpo's deduction—that the evidence suppressor and the falling murder culprit are the same person—to be far-fetched. As evidence, Ranpo pulls out and shows Mushitaro the manuscript's final page, which he found folded and hidden at a gift shop after seeing the manuscript's final page in the red envelope to be a photocopy. He then considers the culprit to be in a hurry of photocopying the last page for a certain reason. Finally, after taking Mushitaro's name, Ranpo identifies him as the culprit of both cases.

The driver instantly stops and points his gun at Ranpo, though Mushitaro urges him to put the gun away, claiming that the detective does not have any concrete evidence that might incriminate them anyway. As the driver asks him to leave, they find themselves surrounded by the police, with Ranpo revealing to have planned it with Poe's help on the other line of the phone call. Minoura attempts to arrest Mushitaro and the driver, only for the latter to invoke his diplomatic rights and show that his legally-carried pistol is not loaded, which averts their arrest. Ranpo allows them to leave.

Along the way, Mushitaro receives a message on a phone and a call from Ranpo, who asserts his will to defeat an ability user like him due to his coworkers' belief in him despite being a non-ability user. The message turns out out to be Poe's novel recreating the Kindaichi murder scene as requested by Ranpo; Mushitaro is transported to the novel world, waking to Yokomizo strangling him in spite. Mushitaro notes on the occurrence's inaccuracy, upon which Ranpo arrives and shows how it truly went, which was Mushitaro strangling Yokomizo to death.

Realizing to be under Poe's ability, Mushitaro remarks that he can easily escape the novel once he, aware of the incident's resolution, declares the facts of the murder case, but Ranpo declares that Mushitaro will end up surrendering with what he tells him. Detailing how the specifics of the manuscript mirror reality's murder case too perfectly, Ranpo deduces that the entire incident is scripted and, ultimately, a suicide under the idea of an ultimate mystery transcending fiction that sparked public interest.

Before his death, Yokomizo was diagnosed with a kind of bowel cancer and planned to finish his ultimate mystery while he could, eventually entrusting Mushitaro to be the mystery's and his killer. Mushitaro then notes Ranpo's deduction to be correct, though Ranpo, making use of the last page smudged with droplets, essentially deduces the droplets to be Mushitaro's tears while killing Yokomizo, pointing that this can overturn the assumed motivation once exposed.

Claiming to assimilate Fyodor's methods himself in order to further protect the Agency, Ranpo threateningly urges Mushitaro to surrender if he does not wish to publicize his deduction and besmirch Yokomizo's final wish. In defeat, Mushitaro turns himself in to the police. Minoura informs Ranpo that evidence in favor of Kunikida's release have started to surface, and Poe tells him that the body double who fell off the tower was only given to him by Fyodor, making it possible for Mushitaro to have never killed anyone save for Yokomizo. Before taken away, Ranpo refers him to a Special Division agent in risk of getting their cover blown, reminding Mushitaro that he would help him land a job should he ever need one.

Ranpo burns the last page of the manuscript, while Mushitaro and the police car carrying him are stopped along the ride. The police driver then gets shot at point-blank range by a uniformed officer who discards his disguise and introduces himself as Nikolai. A subordinate of Fyodor, Nikolai announces the incoming arrival of the five-team terrorist organization, the Decay of the Angel. Mushitaro grabs the police car's radio transceiver and warns Ranpo not to take the Agency's next case at any cost, subsequently getting cut off by the successive gunshots.