Chūya Nakahara vs. Ryūrō Hirotsu

Chūya Nakahara vs. Ryūrō Hirotsu is a battle fought between Sheep leader Chūya Nakahara and Port Mafia member Ryūrō Hirotsu at Suribachi City.

It happened during a preliminary investigation led by Osamu Dazai together with Hirotsu on the alleged appearance of Ōgai Mori's deceased Mafia predecessor.

Prologue
Dazai and Hirotsu arrive at Suribachi City by order of Mori to investigate a rumor that has been going that a certain individual was sighted at the area. Hirotsu accompanies Dazai in which upon arriving, tells Dazai the history of the place. Meanwhile, Dazai is reading the The Complete Suicide. Hirotsu further warns Dazai to be careful since the area is a state of conflict, considering that the Port Mafia has currently three enemy organizations, namely Takasekai, GSS, and the Sheep.

Suddenly, Dazai gets a call from Mori and tells him that he will report the details back. In the middle of their conversation, Dazai is attacked by Chūya, the leader of the Sheep. After attacking Dazai, he gives him two options: die now or die after giving him information about Arahabaki they are investigating on.

Battle
In the middle of interrogating Dazai, Hirotsu tells Chūya to surrender. Armed mafiosi also surround him, but Chūya remains unfazed upon knowing that he can overcome their guns with his ability. Hirotsu then ends his warnings for the adolescent and prepares to activate Falling Camellia. Dazai informs Hirotsu that Chūya can manipulate gravity, to which Hirotsu tells Chūya about his repulsion ability. After their banter, Chūya and Hirotsu charge at each other.

Hirotsu grabs onto Chūya, but the latter uses his ability to swiftly counteract it and kicks Hirotsu multiple times mid-air. Upon landing backwards, Chūya once again charges at and attacks Hirotsu with kicks, keeping his hands hidden in his pockets. The mafioso pulls out his pistol, but Chūya quickly lands a gravity-enhanced kick that shatters its barrel. Chūya then kicks Hirotsu's shoulder and holds him down, while Hirotsu similarly grabs Chūya's shoulder, claiming that he has caught him.

Dazai touches his neck from behind and nullifies his ability. Hirotsu then places his hand towards Chūya's chest and blasts a shockwave that sends both Chūya and Dazai flying backwards. Though Hirotsu directed his attack that must have only blown Chūya away, Dazai explains that the latter kicked him at the instant of the shockwave to release himself from Dazai's touch, upon which Chūya activated his ability to fly backwards unscathed. Chūya jeeringly rushes at them at a rapid speed, but the battle is soon thwarted by an explosion.

Aftermath
The blast sweeps everyone and everything within its immediate radius. Dazai manages to glimpse at the source of the black flames, who turns out to be the previous Mafia boss apparently resurrected. In the end, the black flames engulf Suribachi City, marking the explosion as the most recent incident regarding the Mafia boss' rumored appearance. Afterwards, Chūya is restrained and brought before Mori in the Mafia base.

Differences Across Media
Primarily, Dazai and Hirotsu are accompanied by various mafiosi in the light novel and manga, while the anime depicts only the two of them encountering and engaging Chūya at Suribachi City. Moreover, it is shown in the anime that Chūya lands successive attacks at Hirotsu after the latter blows him and Dazai with his ability, while it is implied in the light novel and manga that Chūya merely rushes towards the Mafia members before getting caught up in the previous Mafia boss' reappearance and explosion.