Naomi Tanizaki/Synopsis

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Port Mafia Arc
Naomi is taken hostage by a bomber at their Agency office. With the help of Atsushi Nakajima and Doppo Kunikida, the bomber was neutralized, but he managed to activate the bomb. Having no choice, Atsushi pushed Naomi away and covered the bomb with his body.

When the bomb didn't activate, it was revealed all to be an act to test Atsushi. Naomi quickly hugged the bomber, who was her brother and overly excited how good he was while acting as the villain. She liked being tied and threatened and wanted them to continue that when they get home.

Later at Café Uzumaki, Atsushi couldn't believe Naomi and Junichirou were siblings, but she assured him. Atsushi ended up having to guess the members' previous jobs and he guessed Naomi and Junichirou were students and they confirmed. As they received news about a client, they all went back to the office.

Hearing the client request, Kunikida assigned Atsushi and Junichirou to the job and Naomi decided to join to, so she can be with her brother. As the client led them to a dead-end alley, she revealed it was a trap and started gunning them down. Naomi stood in front of Junichirou and protected him with his body, who then in anger fought the woman, but was defeated by Akutagawa. Later, she is presumed to be treated by Akiko Yosano after being brought back to the Agency.

While the Agency works on a request from a ministry officer, the Agency learns about Atsushi's kidnapping by the mafia. Though Tanizaki suggests they save him, Ranpo reasons out why they have no reason to do so. Worried for Atsushi, Naomi brings in the President himself to make a decision. In the end, Fukuzawa puts all work on hold and orders the Agency to help bring back Atsushi within three hours.

After 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 Guild Arc
As the Guild leader Francis Scott Key Fitzgerald and two members arrive at the Agency, Naomi serves Fitzgerald some refreshments. He marvels at the novelty of his chinaware cup, to which Naomi chidingly remarks that it came from their nearby ceramic store.

The next morning, Naomi accompanies Atsushi and Tanizaki to look for Kenji Miyazawa, who has gone missing after seeing the visitors out of the Agency building. Eventually, Naomi vanishes in plain sight, which is caused by the Guild's Lucy Maud Montgomery. As she brings them to her dimension, Lucy shows Naomi and Kenji imprisoned in her secret room. When Atsushi and Tanizaki later defeat Lucy, Naomi and the other prisoners are released after Lucy deactivates her ability and lifts the dimension.

After the incident, Tanizaki serves some baumkuchen to Naomi for breakfast. As Tanizaki reads the metropolitan police's records on Kyōka, he tells Naomi on how her parents were murdered.

Eventually, as the Agency, Port Mafia, and the Guild engage in a three-way war, Naomi and Kirako Haruno retreat into hiding in a safehouse. Naomi catches Haruno doting upon her cat named Mii-chan on her laptop; upon noticing Naomi at the side, she quickly returns to work. They then learn about a cruiser explosion near the Yokohama commercial port, which Haruno expounds to be owned by a private company. Naomi thinks that the company might be the Guild's and that the explosion might have been caused by someone from the mafia. Haruno then contacts and warns Fukuzawa, thinking that the Agency might be in trouble next, while Naomi hopes that her brother is safe.

Naomi and Haruno are soon contacted to evacuate as soon as possible, after discovering that two Guild members are after them. As Haruno frantically tries to gather her possessions, including her bottles of wine (which she actually downed in one sitting the previous night) and her curling iron (which she threw out the window while intoxicated), Naomi reckons they leave at once, believing that the Agency and her brother shall arrive soon to rescue them.

However, Naomi notices the Guild members near their lodging, so Haruno recommends that they use her car to escape. As per Naomi's suggestion based on what she learned from Osamu Dazai, they escape through the staff passage and utilize a staff vehicle instead of exiting through the parking lot. Using the keys Naomi swiped from a waitress, she tosses them to Haruno, upon which the latter remarks how Naomi make a great agent possible more capable than her brother, more so if she were an ability user.

They manage to get away from the location, but their escape is soon thwarted when Steinbeck uses his grapevines to trap their vehicle. Steinbeck then greets the clerks and explains how his ability works. Afterwards, he tells them his motive of working for the Guild, stating how he would gladly perform the Guild's undertakings – no matter how much they view it as "evil" – as long as his job helps aid his family financially.

As Steinbeck crushes their vehicle, Lovecraft notices how snow is falling at such a strange time. Kunikida emerges from behind him and shoots the two Guild members, causing Steinbeck to loosen his grapevines' grip on the clerks' vehicle. Tanizaki then breaks Naomi and Haruno out of the vehicle and asks them to flee immediately to a passenger train at the foot of the hill.

During their escape, Haruno gets captured by Steinbeck's grapevines once more, after which Naomi gets caught as well. Eventually, after Tanizaki devises a way to crash a truck onto Steinbeck and Lovecraft, the grapevines collapse and allow Naomi and Haruno to chase the passenger train, where they successfully get onboard.

Inside, Naomi assures Haruno that they are safe at the moment, upon which they soon encounter a mysterious child. As the train arrives, they introduce Atsushi to their acquaintance, who bumps themself on Atsushi and pulls up their sleeve to reveal various razor blades on their arm. Unbeknownst to him, Atsushi soon gets immersed in a curse, which turns out to be Q's ability. Seeing his companions turn hostile against him, Atsushi defends himself by using his tiger strength; he attacks Haruno after strangling him and later chokes Naomi in the process.

Dazai arrives and asks Atsushi to come to his senses. He realizes that he was the one cursed after all rather than the other way around, noticing the traumatized clerks from his attacks. As he experiences a breakdown, Dazai slaps him out of it and lectures him not to pity himself, lest his life shall be an unceasing nightmare. Dazai then announces that they must move onward with their counterattack.

Later, Naomi is among the other Agency members who proudly witness Kyōka pass her entrance exam. Eventually, Naomi and the other Agency members welcome Kyōka as their newest member. Kyōka later calls for Naomi and Haruno per Atsushi's request, who apologizes to them for what he unintentionally did during the Q incident. Naomi and Haruno appease Atsushi's worry and have long forgiven him, though Tanizaki looms behind Atsushi and asks why he has never heard of anything about what happened to his sister, much to Atsushi's uneasiness.

Cannibalism Arc
Naomi is with Haruno at her apartment twelve hours before the virus outbreak. She stops Haruno from going outside to look for her cat who hasn't come back in two days. She wonders that Haruno's cat always disappears whenever past incidents occur and it was dealt before it became truly dire.

In the aftermath of the incident, Naomi attends a banquet held by the Agency at a luxury liner given to them by Fitzgerald. She and the others then approach Ranpo, who tells his co-members about their punishment for disobeying the President's order not to fight with the mafia.

Plot
Naomi is taken hostage by a bomber at their Agency office. Akutagawa quickly uses Rashomon to rip the bombs apart, attacking the bomber and pinning him into the wall. Akutagawa prepares to kill him when everyone reveals its an entrance exam, Akutagawa freezes when he figures out the hostage and the fake bomber are siblings. Naomi informs Akutagawa that she willingly offered to be the hostage and that Tanizaki and her were very close in a flirtatious manner.

Upon learning that Akutagawa is finding his sister, Naomi asks if Akutagawa has an idea of where his sister could be. Akutagawa says that no matter if she is dead or alive, he will find her. Naomi chuckles and reassures Akutagawa that if he is searching for his sister, there isn't any other organization in the world that is more suitable to help him. Saying that after all, that person is in the agency. Naomi says that the agency can certainly find Akutagawa's sister and that they should get going to introduce Akutagawa to the world's greatest detective.

Naomi is then seen later with the other agency members approaching Ranpo to ask for his help in finding Akutagawa's sister.