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, 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 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.

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.