Atsushi Nakajima

The protagonist of the series. An 18-year-old boy known for a distinct tuft of hair hanging on the right side.

Birthday: May 5. Height: 170 cm. Weight: 55 kg. Blood type: AB. Likes: tea rice, cats, chameleons, Yokohama. Dislikes: himself, the orphanage he used to live in.

Though he's timid enough to be called "the coward of the West" at the detective agency, he is kind-hearted and sometimes takes bold actions to protect others, even at the cost of his own life.

He was expelled from the orphanage and was wandering around Yokohama in a state of hunger when he saved Dazai, who had jumped into the Tsurumi River. This incident led to him learning about why he was kicked out of the orphanage and his special abilities, leading him to work for the Armed Detective Agency. Initially, he lacked confidence and was pessimistic, but he grew through various experiences.

He was abused by the staff at the orphanage, causing him trauma. Because his existence was constantly denied, he came to believe that no person is without purpose. He empathized with Kyouka, who had a similar background, and even felt remorse for not being able to find a happy way to live for Montgomery, an enemy. When he understood the true intentions of the orphanage director he had hated (voiced by Hiroshi Naka/played by Keisuke Minami) during an investigation into a traffic accident involving the director, he cried.

According to Fitzgerald, he is the "beetle" necessary for finding the "Book." For this reason, a high bounty (7 billion yen) was placed on his head by the Guild, and he was targeted by the Port Mafia.

Initially, he couldn't remember or be conscious of himself from the start of his transformation until he returned to human form. He didn't realize why he had been kicked out of the orphanage, or that he was a "tiger" or a gifted person, until he met Dazai and others.

After leaving the orphanage, he lived as a homeless person, leading him to develop a strong attachment to money. Later, he was persuaded by Dazai to start living with Kyouka at the detective agency dorm.

During the outbreak of the three-way war, he acted alongside Dazai. After parting with Dazai, he met up with Naomi and Haruno but fell under the control of Q's ability and was saved by Dazai. He then encountered Fitzgerald on the streets but escaped with Kyouka, who suddenly appeared but was captured on the wharf and taken to the Moby-Dick. There, he learned about the "Yokohama Incineration Operation" but managed to escape with Montgomery's help. Though he was shot down by Twain on his descent to the city, he thanked the tiger in his heart, leading the tiger to save him and allowing him to deliver Q's doll to Dazai successfully.

He then reboarded the Moby-Dick, and together with Akutagawa, challenged and defeated Fitzgerald to stop its crash.

When Dostoyevsky's plan to pit the Armed Detective Agency against the Port Mafia was revealed, he tried to follow Fukuzawa's order to avoid conflicts with the Mafia and pursued Dostoyevsky himself with Kunikida. He infiltrated Dostoyevsky's hideout with Akutagawa, and despite their bickering, they pursued Pushkin. They were briefly stopped by Goncharov but captured him with a new joint technique. Akutagawa then challenged him to a rematch in six months, under the condition that Akutagawa would not kill anyone during that period.

After the Armed Detective Agency was falsely branded a criminal organization by the "Decay of Angels," he acted with Kyouka. He requested help from the new Guild's Fitzgerald, exchanging their treatment of Mitchell using Yosano's ability for help finding Oguri with the "Eye of God." They rescued Oguri, who revealed hope in the "reverse page." He then, along with Ango, who cooperated with Dazai, and Montgomery under Ango’s protection, infiltrated the Sky Casino to capture Sigma, the general manager who knew the whereabouts of the "page." After a battle with Yosano at the casino, he briefly caught Sigma, but Sigma fell after being hit by Grace's blood bullet. Through Sigma's touch, he learned the location of the "page" and that "Kamui," the mastermind of the "Decay of Angels," planned to assassinate the detectives, but was saved by Ranpo.

Following Ranpo's instructions, he assisted in smuggling themselves with the "Hunting Dogs" leader Fukuchi but recognized "Kamui’s" true identity, forcing him to retreat into Poe's novel with Fukuchi's slash. He faced Fukuchi with Akutagawa, but their only chance was thwarted by "Time Traveler," leading to Akutagawa’s sacrifice. Escaping thanks to Akutagawa's last effort, he conveyed critical information back.

In Poe’s alternate detective agency space, under Ranpo’s guidance, he attempted to stop the delivery of the "Grand Directive" and the plan to kill Bram Stoker. At the airport, while searching for Bram and Fumi, he encountered Yosano again, trying to secure her cooperation with video evidence left by Tachihara, but she sided with Fukuchi knowing their intentions. After hearing their true goal, unsure of whether stopping them was right but still moving ahead, resolving to find Fukuchi. He then battled Akutagawa, who had become a vampire.

Tiger Beast

A special ability that transforms him into a very large white tiger. In this form, his body becomes as tough as to be impervious to bullets and moves with incredible speed, and any part of his body that is lost is rapidly regenerated. His claws even have the power to tear through other abilities. However, a complete transformation makes him lose control.

After joining the agency, Fukuzawa's ability allowed him to transform just parts of his body, drawing out partial abilities to enhance his physical capabilities and healing, enabling him to control them at will.

The ability's name is derived from the short story "The Moon Over the Mountain."