Doppo Kunikida and Jun'ichirō Tanizaki vs. John Steinbeck and Howard Phillips Lovecraft

Doppo Kunikida and Jun'ichirō Tanizaki vs. John Steinbeck and Howard Phillips Lovecraft is a battle fought between Armed Detective Agency members Doppo Kunikida and Jun'ichirō Tanizaki against the Guild operatives John Steinbeck and Howard Phillips Lovecraft during the three-way gifted organizational conflict.

It happened on the road during the getaway escape of Agency clerks Naomi Tanizaki and Kirako Haruno from their hiding location that was leaked by the Port Mafia to the Guild as part of their strategy.

Prologue
After Chūya Nakahara reveals that the Mafia has leaked the Agency clerks' hiding spot as bait to lure in the Guild, Yukichi Fukuzawa instructs his agents to have the clerks evacuate their lodge. He also contacts the on-standby Kunikida that he and Tanizaki are to face the Guild soon. Meanwhile, Steinbeck and Lovecraft are dispatched by Francis Scott Key Fitzgerald to abduct the Agency clerks as part of their plan to minimize the Agency forces regardless of the probability that it is a trap.

Naomi and Haruno begin evacuating their lodge, exiting through the staff passage door rather than the front door, an unexpected tactic previously taught by Osamu Dazai to Naomi. She also swipes a waitress' car keys and lets Haruno drive. However, Steinbeck traces their getaway car and traps them with his grapevines.

Battle
While Steinbeck explains his motives for completing his missions for the Guild, Lovecraft notices snow falling, from where Kunikida appears behind him and shoots at Lovecraft and Steinbeck's grapevines. Tanizaki rushes to free Naomi and Haruno from the car's grapevines and instructs them to head down the cliff towards a passenger train that they have asked to wait within five minutes.

Steinbeck then acknowledges how the unreliable source's tip is indeed a trap, while Kunikida holds him at a distant gunpoint and keeps an eye on him from controlling his grapevines to buy the clerks enough time. Steinbeck quickly launches his grapevines towards him, which Kunikida shoots, but he is soon rid of his pistol and his arm restrained with grapevines.

Steinbeck then expresses his anticipation on Kunikida's thinking that he is to keep him at bay within five minutes, a predictable action made by oversimplifying situations. In response, Kunikida – using the same line of thought that Steinbeck must not have been expecting – brings out a piece of notebook page from his pocket pre-written with and materializes a pistol. He shoots at Steinbeck's grapevines and rushes towards Steinbeck to flip him. Kunikida then rips out the grapevines on him and Steinbeck, harming the latter in turn.

As Kunikida chides them for their atrocities in a foreign country, Lovecraft stands back up and looms behind Kunikida, getting scolded by Steinbeck for taking his time. Kunikida shoots him, but Lovecraft seems impenetrable against his bullets. Kunikida immediately asks Tanizaki to cover them with Light Snow, only to be restrained quickly by Lovecraft's tentacles, turning the tables on them.

Steinbeck tracks down the clerks using his grapevines once more and successfully entangles them before boarding the passenger train. He then humors Tanizaki that they shall be borrowing his sister, greatly provoking Tanizaki. Kunikida questions how they can possibly ask for understanding their misdeeds, but Steinbeck claims that moralist detectives like them would not understand their work. As Steinbeck notices a truck approaching nearby, Tanizaki mutters that nothing, even morals, can ever compare to Naomi's importance to him.

With the truck not stopping, Steinbeck soon deduces that the driver must be thinking that their direction is part of the road. As Tanizaki darkly declares that he shall gladly reduce the world to ashes for Naomi's sake, the truck crashes at Steinbeck and Lovecraft, freeing Kunikida and Tanizaki (as well as Naomi and Haruno) from their restraints.

Aftermath
Naomi and Haruno manage to board the passenger train, while Kunikida and Tanizaki retreat behind nearby trees. Steinbeck and Lovecraft recover from the crash and attempt to chase them, but they are soon surrounded by the police, as the detectives have earlier notified, and arrested. Later, Kunikida contacts Atsushi Nakajima and Dazai to await and soon regroup with Naomi and Haruno from the passenger train.

Manga and Anime Differences
The anime does not show Kunikida harming Steinbeck's grapevines and him in turn, unlike in the manga where Kunikida does so. He merely flips him that causes the grapevines trapping the clerks' vehicle to collapse to the ground and holds him in gunpoint.