Atsushi Nakajima vs. Ryūnosuke Akutagawa (Alley)

Atsushi Nakajima vs. Ryunosuke Akutagawa is a battle fought between Armed Detective Agency newcomer Atsushi Nakajima and Port Mafia attack dog Ryunosuke Akutagawa during the bounty hunt for Atsushi as the weretiger wanted by the Mafia.

It happened upon Akutagawa's intervention of the battle between his comrade Ichiyō Higuchi against Agency member Jun'ichirō Tanizaki in a secluded back alley.

Prologue
After Tanizaki collapses due to Akutagawa's attack, the latter introduces himself as a Port Mafia member alongside his fellow mafioso, Higuchi. Akutagawa hostilely slaps her for carelessly shooting at their opponents despite orders to capture the weretiger alive, for which Higuchi apologizes. Atsushi expresses confusion at the events unfolding, so Akutagawa enlightens him that their target has always been him from the beginning, with his subordinates merely caught up in the shootout out of his misfortune that he brings upon others.

As Atsushi is taken aback with the memories of the orphanage spiting him as a bringer of calamity due to his existence, Akutagawa unleashes Rashōmon as a warning for Atsushi to surrender, promising to bite off his leg if he resists. The petrified Atsushi wonders whether he truly brings misfortune by simply being alive, but Tanizaki weakly urges him to run away.

Battle
Recalling Doppo Kunikida's counsel that he must avoid anything that smears the Agency's reputation as part of the organization, Atsushi rushes towards Akutagawa while avoiding Rashōmon, grabs Higuchi's submachine guns nearby the mafioso, and immediately fires at Akutagawa. However, Rashōmon devours the space between Akutagawa and the bullets, rendering gunshots and even fire unable to harm him. Fulfilling his earlier promise, Akutagawa launches Rashōmon and cuts off Atsushi's right leg.

Atsushi's memories at the orphanage flood him once more, with its director reprimanding him for crying, a right he claims Atsushi does not deserve as an orphan. Amidst all the rejections and spurns he experienced in his childhood, Atsushi becomes determined to fight back, transforming into his tiger form and regenerating his severed leg.

The tiger charges at Akutagawa, while the mafioso retaliates with Rashōmon. To his surprise, the tiger instantly and efficiently regenerates itself despite Rashōmon's attacks. Higuchi tries to aid Akutagawa, but he stops her from interfering. Akutagawa notes at the tiger's quickness, barely shielding himself at such short notice with Rashōmon: Spider Thread. Higuchi shoots at the tiger, but the tiger's impenetrability renders her attacks useless. Akutagawa is then forced to launch Rashōmon: Agito to cut down the tiger's body.

Afterwards, the tiger's body begins to dissipate, courtesy of Tanizaki's Light Snow that made the mangled tiger an illusion. The real tiger rushes at Akutagawa from behind out of an illusory plane; Akutagawa amusingly prepares to strike it with Rashōmon: Murakumo, while the tiger unstoppingly runs at Akutagawa. Osamu Dazai immediately arrives in between them and nullifies both their abilities with a simultaneous touch to halt the battle, much to the mafiosi's surprise.

Aftermath
Dazai reveals having implanted a listening device in Higuchi's pocket back at the Agency, having seen through her scheme since the beginning. Higuchi threatens Dazai that they cannot leave unscathed, but Akutagawa stops Higuchi and merely warns Dazai that the Mafia shall have the weretiger in due time, explaining that a bounty of ¥7 billion is placed on Atsushi.

Akutagawa proceeds to declare war on the Agency if they choose not to hand Atsushi to them, which Dazai dryly challenges them to do if they dare. Higuchi angrily looks down on the Agency, which she compares to be but puny to the Mafia's extensive control over Yokohama's underworld, bent on burning down the Agency within three days' time. Dazai claims that he knows much about them, since he himself, as Akutagawa notes, is a former Port Mafia operative after all.

Atsushi, Tanizaki, and Naomi Tanizaki are later brought back to the Agency and treated by Akiko Yosano. As he awakens, Atsushi is advised by Kunikida to think about what he can do should the Mafia return once again to capture him. Meanwhile, Tanizaki tells his fellow members about having been dissected by Yosano four times before making a complete recovery from the incident.