Kenji Miyazawa/Synopsis

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Armed Detective Agency vs. Port Mafia Arc
Kunikida had called Kenji and some other members to come to a warehouse, where Dazai said a man-eating tiger will appear. As they came, Dazai had already defeated the tiger and explained it was Atsushi and the tiger transformation was his ability. Kenji wonders what they will do with Atsushi and Dazai explains he wants him to join their agency.

After some time during the Black Lizard attack on the agency, Kenji is present in the office, but the agency easily took down the attacks. Kenji wonders what they will do with them and Kunikida tells him to just threw them out of the window and Kenji proceeds to throw them out one by one.

Following the fight between Atsushi and Akutagawa at the cargo ship, Kyōka Izumi is brought to the Agency office, and Naomi is among the members playing with her. Atsushi, worried that someone like Ranpo might not forgive her crimes, soon finds out that Ranpo himself enjoys playing with her the most, even buying her some snacks.

The Agency is then given a case to investigate a car explosion. After the police leave the office, Kenji states that city polices sure are busy since they leave without having tea. Kunikida then asks Kenji if the police from his home have free time. Kenji then replies that everyone knows each other in his village. The policeman's job was to only fix a pump well, rescuing cats from chimneys, and tasting the first year's watermelon. Kunikida then asks what if someone commits a crime to which Kenji replies that the perpetrator will be tied up and thrown into a cliff. He then also states that he does not really understand the concept of money. Kunikida then offers Atsushi to investigate the case.

Kenji accompanies Atsushi to investigate the case and goes to the Yokohamabashi Shopping District to gather information. Kenji encounters a man he knew and asks him if he knows anything about the car explosion. The man then replies that some folks bought a load of fertilizer and Kenji concludes that it must be nitrogen fertilizer used to make bombs.

Kenji and Atsushi then decide to go to the place of the gang in question and asks them if they are responsible for the bomb explosion. Hearing this, Atsushi then tells Kenji that even though they may be the ones who did the explosion, he doubts that they will admit to it. Kenji then replies that if they are sincere with their inquiries, they will respond.

After arriving at the place, Kenji then asks the folks if they are the ones responsible for the bomb explosion, however they reply that they do not know anything about it. Hearing their reply, Kenji then thanks them and proceeds to leave. After leaving the place, Atsushi exclaims that they are obviously the ones that cause the explosion however Kenji says that he never fails to communicate with others. Kenji then initiates to go eat first before going back to the office.

While heading back to the office, they were blocked by the gang members they asked before and tells them that they might have found a proof since they left early. Kenji then thanks them for telling the truth and tells Atsushi that everyone in his case confesses like that. He was then attacked by a gang member by a pipe causing him to fall. However, he gets back up easily and attacks the gang members. Kenji soon defeats all of the gang single-handedly using his ability. He and Atsushi then eat at a restaurant; after getting full, Kenji takes a nap.

The Guild Arc
The Guild leader Francis Scott Key Fitzgerald and his two subordinates arrive at the Agency office. He wishes to buy the Agency to acquire their skilled business permit, but Fukuzawa refuses his offer. As Kenji soon escorts the three visitors out the building, Lucy compliments his hat, after which he vanishes inside the elevator.

The next morning, Lucy traps Atsushi, Jun'ichirō Tanizaki, and other civilians to her dimension. She also shows Kenji and Naomi Tanizaki imprisoned in her secret room, who can only be freed if they defeat the gigantic creature, Anne. When Atsushi and Tanizaki later defeat Lucy, Kenji and the other prisoners are released after Lucy deactivates her ability and lifts the dimension.

Later, Kyōka is given a mission by the Agency, during which mafia executive Kōyō Ozaki arrives to eliminate Atsushi and retrieve Kyōka. Kenji and Kunikida later arrive to flush out the mafia reinforcements, revealing that they have been notified through Kyōka's phone after it rang. As the Agency gets in a standoff with the mafia, two Guild members arrive along with four more other members. In the end, the Guild members overwhelm all the forces, including Kenji and his subordinates.

After Akiko Yosano heals Kunikida and Atsushi, Kenji takes a nap at the Agency office. The Agency later convenes at the Bankoudou Hall, where Dazai explains their strategy against the mafia and the Guild. To make up for their numbers, they shall split into various teams: one defense team and two offense teams. Kenji, Fukuzawa, Ranpo, and Yosano comprise the defense team; Tanizaki is partnered with Kunikida as one offense team; and Dazai is paired with Atsushi as another offense team. Dazai then finishes with their main objective which is to keep their base hidden as possible, after which Fukuzawa declares that they must survive the three-way ability war.

Mori eventually sends Chūya Nakahara to the Agency's base to deliver a message. After Chūya effortlessly obliterates their remotely-activated equipment, Kenji and Yosano are personally sent to meet with the mafioso. With the detectives having figured out his reason for his visit, Chūya discloses that the mafia has laid a bait for the Guild, particularly for Steinbeck and Lovecraft, and coaxes them to grab the opportunity of a perfect ambush on the Guild.

Yosano admits it to be quite an enticing offer, though she and Kenji propose they settle the issue with Chūya right there and then through battle. Kenji launches the first offensive, dismantling a train track railing which he hurls towards the mafioso. Chūya manages to evade the attack and kicks Kenji away, upon which Yosano sneaks behind him for a quick attack. Chūya then activates his ability to stand on the ceiling, much to Kenji's amusement. Fukuzawa later interrupts their clash and inquires about the offer, where they soon find out that the mafia has used their Agency clerks as the bait.

After Atsushi gets abducted by the Guild, Kenji and the other Agency members restrain Kunikida who gets cursed along with most of Yokohama's citizens. Soon after, Kunikida informs them that the curse has begun.

Later, Kenji is among the other Agency members who proudly witness Kyōka pass her entrance exam. Eventually, Kenji and the other Agency members welcome Kyōka as their newest member. When Edgar Allan Poe visits the Agency office, Kenji receives him and asks if he likes to have some drinks while waiting for Ranpo. Poe mutters to himself, upon which Kenji remarks that he cannot hear him amidst the noise. In the end, Poe tells Kenji that he does not need anything.

The Guild Aftermath Arc
Following the battle with the Guild, Kenji and the other drained Agency members are updated by Atsushi about criminal organizations eyeing the Guild's alleged fortune. The next day, he and the others locate a gang that ransacked Café Uzumaki; Kenji easily rips out their supposedly secure door and confronts the gang with the other members. As they return to the café, they are introduced to Lucy, the café's new waitress.

Some time later, Kenji asks for the Agency's second-in-command, whom Tanizaki thinks to be Ranpo (though he rejects such title) or Dazai (who is occupied on thinking how to disrupt Kunikida's schedule). At the end of the day, Kenji and Tanizaki learn from Dazai that the Agency's next president is Kunikida.

Cannibalism Arc
As Fukuzawa is attacked by a masked assassin, Kenji and the others rush to the President's side, where they find him get afflicted with a virus that even Yosano cannot accurately diagnose nor treat. As the mafia arrives at the hospital where the President is taken, Ranpo encourages them, especially asking Kunikida as their interim director to issue his comrades with his orders. As such, Kenji and the rest of the Agency simultaneously guard Fukuzawa's room.

As they face off with the mafia's main forces led by Chūya, Kenji and the others begin to dissipate, revealing it as Tanizaki's illusion. In truth, Kenji had blasted through the wall and carried the President out to safety with the others, rethinking their strategy in their escape.

Kenji and the others soon fetch Kyōka and Tanizaki after escaping from the mafia. Despite their new order from Fukuzawa himself not to fight the mafia, Ranpo persuades them that it is inevitable to fight them after they tried and failed to catch the virus ability user. As such, Kenji and most of the Agency members, except Kunikida and Atsushi, agree to launch a frontal assault at the mafia.

Tanizaki, Yosano, and Kenji head to the mafia headquarters and charge at the mafiosi, managing to break through the first floor of the building. Eventually, a barrage of gunshots rain upon them, forcing them to go on the defense. When the attacks stop, Kenji and the others soon notice Motojirō Kajii walking up to them; to their surprise, the mafioso launches his so-called Lemon Runway, paving the path he walks with lemon bombs. Yosano then calls Kenji and Tanizaki to retreat.

In their search for Fyodor, Kenji and Tanizaki monitor the exits from above the Rats' hideout. Kenji contacts Dazai about the activities happening, such as a horde of vehicles exiting the coal mine. Dazai asks them to ignore it, including the subsequent ones they see. Though Tanizaki panics upon why Dazai does not give the order, Dazai quips that they must not waste their manpower in capturing a demon. Tanizaki soon tells Dazai about a chopper near the site, while Kenji tells them of a lone man on the ground casually walking. Dazai gives the order to capture the lone man; to their dismay, their caught target is not Fyodor.

Eventually, Kenji, the Agency, and the mafia confront Pushkin altogether at the end of the coal mine, leading the Russian to deactivate the virus. In the aftermath, Kenji and the Agency hold a banquet at a luxury liner given to them by Fitzgerald. Tanizaki worries about their punishment for disobeying the President, though Kenji and Kyōka are quite indifferent and rather thrilled given how he describes their situation. They then approach Ranpo after escaping Poe's novel, to which he tells them about their punishment.

In the anime, Kenji and the others apologize to Fukuzawa. Kunikida speaks on their behalf, willing to accept their punishment for disobeying the President's order not to fight the mafia. Nonetheless, the President smiles at them and is grateful for their efforts.

Decay of Angels Arc
A month after the events of Cannibalism, the Agency is conferred the Shikyuu Award for their services in helping preserve the peace and order of Yokohama. Soon enough, Kenji and the others are briefed by Kunikida on a "murder association" known as the Decay of Angels responsible for four gruesome murders of government officials, which allude to the five signs that indicate the imminent death of an "angel" in Buddhism. Fukuzawa orders them to prevent a fifth murder from happening, but Ranpo – remembering Mushitaro Oguri's warning for him not to take their next case – refuses to take the case and storms out of the office.

Nikolai Gogol contacts the Agency holding government officials hostage. As a test solely for them, he challenges them to save the hostages being tied to chainsaw chairs before they activate within 30 minutes or before any external parties interfere. Kunikida contacts Ranpo, who asks them to be careful of the situation, while he follows down a lead. They head to the hostage site, where Kunikida asks Kenji to stop the incoming military police from interfering their operation. Eventually, the Agency finds themselves identified by Justice Vice Minister Tonan as the Decay of Angels and hunted by the military police.

Kenji regroups with the others and blockades themselves from the military police. They are contacted by Ranpo, who warns them about the Book's power spurring the current events. He asks them to avoid capture at all costs despite their innocence, but their conversation is cut short as Ranpo jumps off a building to escape from the police at his end.

The military police fires sleeping gas at them, forcing them to commit suicide as the operatives barge in the room. To their surprise, Yosano resuscitates her four comrades using her ability to take out the police altogether. They soon change into the operatives' riot gear and escape from the building.

Plot
Kenji and Yosano arrive at the agency office when the agency members are in the middle of persuading Ranpo to help Akutagawa find his sister. After Akutagawa acquires the president's and Tanizak's stamp of approval, he approaches Akutagawa for his individual work and tells that he needs Akutagawa's help with basic farm work.

The next day, Kenji and Akutagawa are at a rice field. Kenji proceeds to teach Akutagawa how to plant rice. Kenji says that it will take two weeks at most to finish the work. Despite the long period, Akutagawa accepts to do the job since he is the one who says he'd pay the price. Kenji and Akutagawa continue to work in the rice field. However, on the tenth day, the rice became withered. Akutagawa then spots a truck dumping waste containers near the rice field and attacks it. Kenji stops him and tells him that killing people is bad and as long as they have the waste containers, the agency can track them. The next day Kunikida informs the two of them who is behind the illegal dumping and reveals that it is a industry-leading pharmaceutical company in the world of mass-produced pharmaceuticals. Kenji then smiles says that it can't be helped but at least the rice paddy is fine and tells Akutagawa that they should continue the rice planting.

He then later on appears at the pharmaceutical building with Tanizai and Oda to stop Akutagawa from killing the president of the company. After stopping Akutagawa, they went back at the ricefields. Kenji started talking and describes the whole event as adorable since natural disasters like floods, frost, drought, and infestation are more brutal and irrational. He further shares to Akutagawa that due to the disasters, al the hard work that has been spent for most of the year suddenly disappeared overnight. He reassures Akutagawa that they still have time and if the agency manages to prove that it was illegal dumping, they can sue them, unlike natural disasters.

Kenji starts to talk that some things grow and disappear just like how grass grows and withers and how animals give birth then die. Kenji then tells Akutagawa that by living on the land, one can understand that nature is made up of halves and that bad things and good things are all part of nature. Kenji, with a smile, tells Akutagawa that that the reason why Akutagawa still has his half and reassures him that he will find his sister. Kunikida then arrives at the ricefields only to find Kenji and Akutagawa bonding. Back at the agency, Kenji gives his stamp of approval to Akutagawa for accomplishing Kenji's request.