Doppo Kunikida/Synopsis

Background
Alongside working in the Agency, Kunikida previously worked as a cram school tutor for maths, working part-time on the weekends before turning 20. He paired this with college studies, but later dropped out to dedicate full-time to the Agency.

Some point afterwards, Kunikida focused on a terrorist known as the Azure King. Although working alongside authorities, miscommunication ultimately ended in multiple detectives' deaths, including Rokuzo Taguchi's father. Due to his guilt, Kunikida took up trying to support Rokuzo later in life, but both suffered from a strained relationship, with Rokuzo wanting little to nothing to do with Kunikida.

At some point, Kunikida handled a case involving a high school student setting bombs up on school grounds. He attempted to talk the boy out of this terrorist mindset, but later learns he failed.

During Osamu Dazai's entry into the Agency, Kunikida's tasked with deciding whether or not Dazai is meant for the Agency. Yukichi Fukuzawa orders him to kill Dazai if Kunikida determines Dazai is a danger. An order that, despite Kunikida's faith in Fukuzawa, begins to shake Kunikida's faith in his ideals.

The two work on a serial kidnappings case, and Kunikida enlists Rokuzo's technological skill to find solid leads. Kunikida and Dazai later rescue Nobuko Sasaki from drowning in a tank. Unfortunately, several other kidnapped victims, locked in a gas chamber, perish. Security cameras recording the incident were leaked, an image of Kunikida failing to save the victims published in the newspaper.

This further strains Kunikida's ideals, however he presses on, hoping Sasaki's ordeal and further leads will finally lead them to the true Azure Messenger.

Unbeknownst to Kunikida, Dazai later has Rokuzo look into Sasaki's claims, leading himself and Kunikida to an abandoned building. When Rokuzo arrives, Kunikida denies the thought of him the Azure Messenger, which Dazai confirms, however, before either he or Rokuzo can clarify the situation, Sasaki appears, shooting and killing the boy. Sasaki confesses to the kidnappings and murders being her doing. She tells Kunikida she and the Azure King were lovers, and now she takes his place to follow through with his ideals, but with this confrontation, she's tired of killing and living altogether, unable to reach those ideals in the first place. Before Kunikida can react, Rokuzo shoots and kills her.

Rokuzo and Sasaki's deaths greatly impacted Kunikida and his view of his ideals. Although he remains true to them, he is constantly haunted by the deaths of those he cannot save, a weight that remains heavy on his shoulders.

Plot
While at a mission, Dazai jumped in the river to commit suicide and then met Atsushi. Kunikida then came yelling at him, but Dazai made him pay for their dinner. While eating, they introduced themselves and Kunikida explained their mission was to capture a man-eating tiger. Upon hearing that Atsushi attempted to run, but Kunikida stopped him. Atsushi explained that the tiger attacked the orphanage he was in and he then got kicked out of it, and now the tiger followed him in the city. Dazai then gave Kunikida a note and went with Atsushi to capture the tiger.

Later that night, Kunikida came to the warehouse where Dazai had mentioned the tiger will appear and had brought some more agency members with him. There Dazai explained the tiger was Atsushi and wanted to welcome him in their organization, which shocked Kunikida as it wasn't Dazai's decision at who joins them.

On the next day, Kunikida found Dazai and Atsushi and again got angry at Dazai. He then explained there was a bomber at their agency office and they all went there. As they were wondering what to do, Kunikida lost to Dazai on rock-paper-scissors and had to confront the bomber, but as the bomber knew who he was, he made Kunikida keep his distance and was careful about his ability. Dazai then made Atsushi face the bomber and act as worthless human and as Atsushi did, Kunikida saw an opening and using his ability took out the bomber detonating device and then knocked the bomber. Kunikida then got in argument with Dazai, which gave a chance for the bomber to escape and activate the bomb. As Kunikida was struggling with the bomber, Atsushi decided to sacrifice himself and cover the bomb with his body. But as the bomb didn't explode, it was revealed all to be an act and test for Atsushi, who was then accepted into the agency by Dazai's recommendation.

At a bar, the group were talking and Atsushi ended up guessing each person's previous jobs. He guessed that Kunikida was an official worker and Dazai corrected him being a math teacher. Then they got a call for a client and went back in the office. As Dazai made a move on the client, Kunikida took him in the other room and beat him up. After listening to the client's job, Kunikida gave it to Atsushi and Junichirou and then warned him that if he sees a man named Akutagawa, to run away.

When Atsushi woke up after Akutagawa's attack, Kunikida was next to him reading his notebook. Kunikida explained that Naomi and Junichirou were fine. Kunikida looked calm, but Atsushi noticed his notebook was upside down and as he told him, Kunikida stood up in shock explaining that in the worse case scenario they get attacked, he will take down the mafia with variety of techniques. Atsushi realized Kunikida was nervous and thought the situation was serious. He decided to leave the agency, so it doesn't get attacked, but the agency still got attacked. As they were gunned down, Atsushi arrived to see how Kunikida took down the last member of the attackers. The agency had easily dealt with the attack and Kunikida was angry at how much money that will cost them to fix all the damages. Another member reminded him it was his turn to go around with gifts and apologize to their neighbours, which annoyed Kunikida as that was the worse case scenario he imagined.

Kunikida was preparing for work, as he arrived few seconds earlier, he waited before entering, but as he entered Atsushi asked for his help and explained that Dazai had eaten some weird mushrooms. Dazai was acting crazy, but Kunikida decided first to do his paperwork. The moment he was done with it, he knocked Dazai as he was annoying him. Later they went to check an anonymous tip and first went to the hideout of Rokuzō, a hacker informant working for the agency. Then Kunikida called a taxi, who was another informant and explained he wanted to show Atsushi their informants. They went to an abandoned hospital following the tip, there they managed to find and save Nobuko Sasaki, but several other kidnapped people go killed with a gas.

On the next day, while Dazai was messing with Kunikida about his ideal woman and having glasses, Kunikida realized something and they called their taxi informant again. In the taxi, Kunikida revealed that the informant was the kidnapper and that he was selling the kidnapped people's organs to the black market. The taxi driver revealed he was being forced into doing this and asked for protection as accidentally he had kidnapped someone from the Port Mafia. In that moment the Port Mafia started gunning them and Kunikida used his ability to help them get out of the car. Akutagawa then came and started fighting Kunikida, but while fighting police sirens were heard and Akutagawa decided to retreat. Later the taxi driver had given them the place his deals were happening and as they went there, they received request from their anonymous tipper about a bomb they need to disarm.

At the agency office, the group were discussing the bomb situation and how to deal with it. Ranpo wasn't available at the moment, so they had to start working on solving the situation without him. Kunikida called Rokuzō asking him to try digging up some information on the bomb equipment they found. Later he went into a cafe were Dazai was speaking with Nobuko. As they discussed the bomb, Dazai asked Nobuko about her opinion and she suggested the culprit was related to Azure King. Dazai then tried hooking Kunikida with Nobuko as he was her type and even revealed Kunikida's type to Nobuko, but she thought it was too much. They received news from Ranpo, as he as done with his case and he told them where the bomb was. Heading towards it, the bomb squad had already found it, but weren't able to disarm it. The three of them received calls from Ranpo, Rokuzō and the president. With the new information they went towards a former defense facility, where they got attacked. Kunikida ended up fighting a man who could put a number on Kunikida and freely control him. As he was no match for him, he saw Dazai struggling with a large man and managed to switch places with him, taking out the man, while Dazai neutralized the other man's ability. Kunikida then recreated the key needed to stop the bomb and they managed to disarm it.

On the next day, Kunikida visited the graveyard, where Nobuko visited him and explained she lied to him, saying that her previous boyfriend had died. As she left, Kunikida was called to the abandoned hospital by Dazai and there Dazai revealed he figured all out and the culprit will come. As Rokuzō came, Kunikida thought he was the culprit, but Dazai explained he probably hacked his email which he used to call the culprit. Nobuko then came and shot Rokuzō, revealing that the Azure King was her boyfriend and that she was the Azure Messenger, and moments later ended up being shot by the dying Rokuzō. Dazai mentioned that Kunikida ideal may one day lead him on the path of the Azure King, but Kunikida assured him, he will not turn like him.