Akiko Yosano vs. Hooded Figure

Akiko Yosano vs. the hooded figure is a battle fought between Armed Detective Agency member Akiko Yosano and a mysterious hooded figure, later uncovered to be a metal mannequin controlled by the Hunting Dog and Port Mafia double spy Michizō Tachihara.

It happened in a Mafia secret base after Yosano, Jun'ichirō Tanizaki, and Kenji Miyazawa separated ways in escaping from the Hunting Dogs and the military police.

Prologue
After the Agency members and the Black Lizard are suspiciously sniffed out by the military police, they come across a hooded figure whom they notice has a Hunting Dog. The figure then attacks both Kenji and Ryūrō Hirotsu along the process, while Gin Akutagawa and Tachihara, along with the other Black Lizard, are overwhelmed by the military police.

Later, Yosano briefly reunites with Atsushi Nakajima and Kyōka Izumi, though she instructs them to escape safely with Margaret Mitchell after the hooded figure follows them. Yosano urges the figure to reveal its face, only for it to show a covered with "正" marks reminiscent of the Soldier's she knew from the past. The Black Lizard commanders soon come to Yosano's aid, after which Gin, Tachihara, and a horrified Yosano manage to hide in a secret, highly secured base.

To their shock, the hooded figure appears before them and incapacitate both Gin and Tachihara with its saber. Thinking that the figure is somehow related to the Soldier, Yosano steels her resolve and accepts to confront her ghost from the past.

Battle
The figure launches various attacks with its saber, which Yosano evades agilely. She soon grabs Tachihara's gun nearby and shoots at the figure, but the figure apparently stops the bullets. Yosano worries that swords, guns, and other weapons do not seem to work against her opponent; before she can think of another plan, the figure manipulates a boat nearby and hurls it towards Yosano.

As the figure approaches her, Yosano retorts that she is no longer alone, since her sins from the past have now been forgiven by both Yukichi Fukuzawa and Ranpo Edogawa. She then clutches the figure, who remotely shoots at her with a gun. However, Yosano instantly heals from her wounds and pins the figure at the barricaded door, which has a bomb prepared by Tachihara for the base's supposed bomb door.

Yosano is ready to accept her punishment at the cost of saving the Agency and decides to detonate the bomb on the figure and herself. To her surprise, the bomb turns out to be a fake, and she finds the figure to be a metal mannequin all along. She deduces that the enemy must have been nearby from the beginning while manipulating the mannequin.

Her calf is soon hit by a blade, afterwards recognizing the mannequin to be close to them before coming to the secret base. The four Hunting Dogs soon personally arrive at the base, much to Yosano's aghast.

She soon realizes that being followed in the Mafia's maze-like underground paths, an enemy who seemingly slipped through doors, and the fake bomb all lead to the fifth Hunting Dog's doing, who turns out to be Tachihara.

Aftermath
Tachihara reveals that the Soldier was his older brother and that he intentionally joined the Mafia as an undercover Hunting Dog spy in hopes of ending up near Yosano along the process. Yosano then asks him to finish his revenge, so Tachihara points his gun at the doctor. In the end, however, Tachihara is unable to pull the trigger on Yosano. He then opts to return to the field; Yosano apologizes to Tachihara for what happened to his brother, leaving Tachihara further conflicted.

Yosano is later arrested and gets due for execution as death penalty, until she eventually gets rescued by Ranpo.