Ryūnosuke Akutagawa and Atsushi Nakajima vs. Ivan Goncharov

Ryūnosuke Akutagawa and Atsushi Nakajima vs. Ivan Goncharov is a battle between Port Mafia member Ryūnosuke Akutagawa and Armed Detective Agency member Atsushi Nakajima against Rats in the House of the Dead member Ivan Goncharov at the height of the Cannibalism operation.

It happened in the midst of the hunt for Alexander Pushkin in the Rats' underground coal mine base. This is the final stand of the Rats before their fall at the allied Agency and Mafia forces, albeit being the first course in the Decay of the Angel' terrorism plot.

Prologue
While approaching the escaping Pushkin, Akutagawa and Atsushi are attacked by a stone giant wielded by Goncharov, the proclaimed chamberlain of Fyodor Dostoevsky. Akutagawa proposes that he and Atsushi take on the ability user quickly in order to capture Pushkin and end the virus once and for all, while Goncharov becomes amused to deal with his guests as a chance of serving Fyodor.

Battle
Atsushi lands a punch towards the stone giant, but the latter uses its palm to block him. Akutagawa mocks Atsushi's weak punch and utilizes Rashomon to sustain various cuts on the stone giant. To his surprise, the stone giant regenerates fully, with Goncharov asserting that his stone giant cannot be beaten no matter how they attack it. As Atsushi prepares to dodge, several stone hands emerge from the ground and hold down Atsushi's feet, who gets hammered by the stone giant once he is immobilized.

Goncharov reminds them that he can control stone and that the very earth they stand on is their enemy. He is also surprised that Atsushi has survived the stone giant's attack unlike many before him and compliments his tenacity. Atsushi notions that taking out Goncharov, rather than attacking the stone giant, is the only way to win. He then turns to Akutagawa, who mutually acknowledges thinking the same plan as him after many times of fighting each other.

The two ambush the stone giant simultaneously. Akutagawa uses Rashōmon as a foothold for Atsushi to evade the stone hands and to propel Atsushi directly in front of Goncharov. Akutagawa then propels Rashōmon into various directions for Atsushi to leap on from different points, confusing Goncharov whence Atsushi would attack. Atsushi attacks from behind, but a boulder is hurled towards him. Goncharov points out that his rapidly spinning stones provide him omni-directional defense.

Akutagawa grinningly entangles and spears Goncharov with Rashōmon, retorting that his words of the earth being their enemy apply to his enemies as well. The stone giant crumbles, while Atsushi recovers from being lured as bait. After a quick banter, Akutagawa initiates that they chase down Pushkin's mine cart, but Atsushi is once again hurled at by a boulder.

Akutagawa notices that the Goncharov he impaled is a clay doll, during which the real Goncharov emerges from the stone giant and reaffirms his allegiance to Fyodor. Atsushi finds himself infected with the virus as well, and Goncharov is pleased at how they played right into Fyodor's hand since the beginning.

With both of them infected with the virus, Akutagawa and Atsushi sink into a quicksand conjured by Goncharov, who leaves and bids his farewell. Akutagawa asks the distraught Atsushi on why he keeps on fighting, to which he responds that he essentially wishes to break free from his deceased mentor's yoke from the past. Satisfied with his answer, Akutagawa immediately wraps Atsushi in Rashōmon.

Goncharov turns back and finds the ground with Atsushi, together with the space around it, dug out. Atsushi suddenly appears behind him and instantly leaps by shaving off the space using his tiger speed enhanced with Rashōmon. The stone giant takes on the offensive, but Atsushi tears through it with his claws.

To Goncharov's shock, the stone giant fails to regenerate; Akutagawa explains that the tiger's Rashōmon-clad claws tear through abilities themselves akin to a divine blade. Merging their abilities together, Atsushi activates Beast Beneath the Moonlight–Rashōmon: Black Tiger's Supreme Claw and presumably defeats the stone giant along with Goncharov himself.

Aftermath
Akutagawa restrains the defeated Goncharov, while the Agency and the Mafia forces easily corner and capture Pushkin. The virus then dissipates on Atsushi and Akutagawa, as well as their leaders. However, Atsushi reports that Fyodor is not in the coal mine; Goncharov then mockingly points out that Fyodor is not even in the hideout in the first place.

Manga and Anime Differences
Akutagawa originally remarks on Atsushi's "pitiful punch" after the latter asserts how the stone giant is rock-solid, but this is omitted in the anime. Moreover, in the manga, Akutagawa and Atsushi simultaneously run towards the stone giant for their ambush attack. In the anime, only Atsushi rushes at the stone giant, and Akutagawa is also hammered down by another stone giant hand, though he later breaks free using Rashōmon.

Later, the manga shows Akutagawa spearing Goncharov once; the anime portrays him impaling Goncharov with various more spears after his initial attack. After Atsushi is infected with the virus, the anime adds him being punched by the stone giant before the two of them sink into the quicksand. When Atsushi gets clad in Rashōmon and instantly leaps near Goncharov, the manga shows the latter summoning a single hand from the stone giant, while the anime depicts two hands from the giant attempting to crush Atsushi.