Atsushi Nakajima and Ryūnosuke Akutagawa vs. Francis Scott Key Fitzgerald

Atsushi Nakajima and Ryūnosuke Akutagawa vs. Francis Scott Key Fitzgerald is a battle fought between Armed Detective Agency member Atsushi Nakajima and Port Mafia member Ryūnosuke Akutagawa against the Guild leader Francis Scott Key Fitzgerald during the three-way gifted organizational conflict.

It happened inside and later on the deck of the Guild's airship Moby Dick minutes before its supposed descent to Yokohama.

Prologue
After Atsushi manages to shake off Akutagawa who is bent on killing him ever since his loss from their previous battle, he arrives at the top-floor executive office to retrieve the control terminal that can stop Moby Dick from crashing into Yokohama. As per Herman Melville's earlier hint, Atsushi finds the control terminal being personally guarded by Fitzgerald, who welcomes and engages Atsushi while sharing his secrets to success with him.

Battle
Fitzgerald offers to give Atsushi a chance to snatch the control terminal from him on three counts; on the second count, Atsushi quickly rushes towards the control terminal, but Fitzgerald anticipates his move and swiftly kicks him on his abdomen. When Atsushi soon gets up from his attack, Fitzgerald admires him for withstanding $10,000 worth of his power. Fitzgerald then takes out $100,000 of his securities in possession and introduces his ability, the Great Fitzgerald, which grants him a boost in power proportional to the amount of his expenditure.

Activating his ability after throwing out his cheques, Fitzgerald kicks Atsushi that sends him flying through the door. He soon voices his premature victory by having captured the mantiger and Moby Dick to crash upon Yokohama, which all adhere to their tactician's strategy. Fitzgerald kicks him on the back and prepares to rip off his limbs to prevent him from further escaping, but Fitzgerald notices Akutagawa's arrival, who ignores Fitzgerald and heads straight to settle his accounts with Atsushi. He expresses his own unfathomable perception towards Atsushi's reckless and conflicting actions, during which Fitzgerald interrupts his ramblings.

Akutagawa strikes him with Rashōmon, though Fitzgerald blocks it with his palm; the mafioso urges Fitzgerald to stay put and wait until he finishes his priority, but Fitzgerald pulls Rashо̄mon towards him and demands a change of order. Fitzgerald requests he prioritize fighting him instead, to which Akutagawa agrees. Akutagawa unleashes beast-headed tendrils and strikes Fitzgerald, but the latter catches them with his bare hands, afterwards lunging to punch Akutagawa and kicking him off a wall. Akutagawa activates Black Wave, but Fitzgerald overpowers him upon spending $500,000.

Atsushi soon lands upon Fitzgerald and spites his perceptions on using his wealth for trampling on the weak. Fitzgerald grabs him off his shoulders and flips him to the ground. He claims that power, including money, can be produced from exploiting the "weak", the kind of people he mentions to be like Atsushi's past self, indicating his knowledge on his rough youth in the orphanage. With Atsushi visibly taken aback, Fitzgerald notices the ship gradually descending; Akutagawa chuckles under his breath and cuts through the floor with Rashōmon, taking Atsushi with him in an escape.

Having barely escaped Fitzgerald, Atsushi attempts to flee from Akutagawa, who catches him by his ankles with his ability. Finally understanding Atsushi's actions and his motives behind them, Akutagawa finds him quite irksome and disappointing that he has become unwilling to kill him, deeming it as a waste that brings him no accomplishment nor honor. He adds that his life is all for the sake of ascertaining accomplishment and victory out of his desire to be acknowledged by Osamu Dazai. Before he can elaborate, Fitzgerald kicks down a wall and locates them.

While Akutagawa and Fitzgerald are clashing, Atsushi spots the nearby cargo elevator to escape to, but Akutagawa follows him shortly before it closes. Akutagawa continues deriding Atsushi and expresses shame for losing to a worthless person such as him before, to which Atsushi angrily claims that he is stronger than Akutagawa who indiscriminately kills for the mere sake of flaunting his skills. Akutagawa finally loses his cool and explains his exasperation towards Atsushi, whom he believes is a capable ability user who has effortlessly acquired Dazai's respect albeit someone who dwells in his tragic past.

The elevator soon brings them to the ship deck, and Fitzgerald welcomes them to their final battlefield. Bent on defeating him to prove his strength, Akutagawa clads himself in Demonic Armor and engages Fitzgerald in combat, allowing him to block and enhance his power against Fitzgerald's strength. Meanwhile, Atsushi taps onto his tiger strength and interferes in their fight, leading the two to launch their individual attacks against Fitzgerald. The latter amusingly remarks that they are quite alike, much to their annoyance that forces them to punch Fitzgerald together.

A weakened Akutagawa reverts his armor back to his coat, while Atsushi plans to take the control terminal as soon as possible. However, Fitzgerald recovers immediately and spends all of his disposable assets for the sake of acquiring the Book to resurrect his deceased daughter and bring his family back together. Faced with the Guild leader's ultimate resolve, Atsushi and Akutagawa decide to momentarily set aside their differences; Akutagawa claim that Atsushi's past no longer have to do anything with him, while Atsushi believes that Dazai must have long acknowledged Akutagawa's power.

Fitzgerald blocks Atsushi's tiger-enhanced punch and Akutagawa's Demonic Armor attack with his bare hands, afterwards tossing them off with ease and agilely kicks down Atsushi. With 59 seconds remaining before the ship crashes to Yokohama, Atsushi and Akutagawa once more attack him, but Fitzgerald easily outmaneuvers them and punches Atsushi to the stomach. Akutagawa holds down Fitzgerald's arm with Rashōmon to enable Atsushi to punch him on the face, but Fitzgerald is unfazed and kicks Atsushi strongly enough to throw him off deck.

Akutagawa catches Atsushi with his tendrils and propels him back on air. He wraps Atsushi's tiger arm with Rashōmon, and Atsushi lands a heavy punch at Fitzgerald with Beast Beneath the Moonlight–Rashōmon: Toramurakumo, apparently defeating him. Shortly afterwards, Atsushi and Akutagawa are evidently drained from their combination attack. To their shock, Fitzgerald remains standing, proclaiming his victory. However, Fitzgerald appears to have finally exhausted all his wealth and falls off the ship deck, bidding his wife Zelda to wait for him and promising to make her happy again.

Aftermath
Atsushi panics about taking the control terminal with Fitzgerald, but Akutagawa immediately hands it to him after swiping it off from Fitzgerald earlier. With three seconds remaining, Atsushi finally shuts down the control terminal and prevent the airship from further descending. However, an external party hacks into the device that resumes their descent, which is eventually taken care of by Kyōka Izumi after she collides the unmanned aircraft she is imprisoned in with Moby Dick and redirects its fall away from crashing into the city. This is soon revealed by Dazai and Yukichi Fukuzawa to be Kyōka's entrance exam to the Agency, which results to her passing it for saving Yokohama.

With Fitzgerald's defeat, Dazai acknowledges Akutagawa's strength, and the three-way gifted organizational conflict ends. The Special Division for Unusual Powers attempts to cover up Moby Dick's sinking near Yokohama (albeit managing to do so partially due to its extensivity), while remaining Guild members go their personal ways after Fitzgerald goes missing from his fall, which has stirred an internal strife within the organization. Fitzgerald turns out to have survived when his ability consumes his $500,000 wedding ring and strengthens his body to narrowly escape death during his fall.

Manga and Anime Differences
The anime relatively lengthens the final battle, which largely differs from the manga. After Fitzgerald spends all his wealth, Atsushi and Akutagawa rush towards Fitzgerald but get blasted away by his overwhelming aura rather than evading an incoming attack at the both of them. Fitzgerald then kicks off Akutagawa then punches Atsushi; the anime omits Fitzgerald blocking both their attacks. With three minutes remaining (rather than less than a minute in the manga), Fitzgerald punches Atsushi on the face and kicks Akutagawa on the stomach. When Akutagawa soon holds down Fitzgerald, the latter punches Atsushi instead of kicking him off.

During Atsushi's final attack on Fitzgerald, the anime further extends their encounter and shows Fitzgerald blocking Toramurakumo, unlike in the manga where Fitzgerald directly suffers from its power. In addition, the anime includes Fitzgerald's assets depicted like stocks plummeting to indicate his wealth gradually declining as his ability consumes it completely.

Trivia

 * In the anime, the control terminal shows Moby Dick's coordinates of "N35:26:01.5 E139:46:12.7". In reality, coordinates bearing 35°26'01.5"N, 139°46'12.7"E belong to a point somewhere in Tokyo Bay, where the Port of Yokohama is situated. This may be the body of water where Moby Dick later sinks after Kyōka crashes the unmanned aircraft to it, though this is never confirmed nor specified.