Dazai

Osamu Dazai (太だ宰ざい 治おさむ, Dazai Osamu?) is a member of the Armed Detective Agency and former executive of the underworld organization, the Port Mafia. He has the Ability named No Longer Human.

The story focuses on a young adult named Atsushi Nakajima, who is the main character. After being kicked out of his orphanage, Atsushi saves a detective named Osamu Dazai, believing he was drowning in the river while his actual intention was suicide. During his interactions with Dazai, Atsushi learns he is a gifted with a supernatural ability capable of transforming him into a berserker white tiger in the moonlight; which was why the orphanage tortured him and kicked him out. Dazai recruits him into the Agency he works for, the Armed Detective Agency, that handles crimes too dangerous for the police to handle. There, he meets many other ability users as they tackle various cases and events taking place in the city of Yokohama, a place teeming with individuals with Supernatural Abilities. Atsushi becomes the target of Ryūnosuke Akutagawa, who is a member of the criminal organization run by Ōgai Mori known as the Port Mafia. Atsushi also recruits the young mafia member Kyoka Izumi upon learning she is being forced to kill.

During Atsushi Nakajima's fights against the mafia, he also meets Francis Scott Key Fitzgerald, the leader of the Guild who placed the bounty on his head. Fitzgerald reveals there is a supernatural book (referred to as The Book) capable of changing reality linked with Atsushi's tiger, hence putting a bounty on the black market. Fitzgerald disregards any superficial damage the Guild might bring to Yokohama in exchange for the book, having an airship named "Moby Dick" destroy the city. However, he is nearly killed by Atsushi and Akutagawa once they join forces while Kyoka stops Moby Dick. Kyoka passes the Agency's entrance exam as a result of doing so.

Another man, known as Fyodor Dostoyevsky, appears, wishing to obtain The Book in order to erase all gifted people. He sets up a fatal clash between the detectives and the mafia using a virus ability user from the group that he leads, Rats in the House of the Dead. Natsume Soseki, who is the creator of the collaborative Tripartite Framework, stops the fight. While Atsushi and Akutagawa corner the virus' originator, Dazai manages to arrest Dostoyevsky with Fitzgerald's help. However, Dostoyevsky is later revealed to have orchestrated his own imprisonment in order to lead his followers.

Pages of The Book are later found by Dostoyevsky's other group, The Decay of the Angel, which uses its powers to frame the Detective Agency for a murder case. Dazai is imprisoned for his past crimes and is placed in a cell near Dostoyevsky while the government sends its military forces known as the Hunting Dogs to execute the members of the Agency. As the Agency faces defeat, they form an alliance with Fitzgerald and later the mafia in exchange for one of their members (to the mafia). Across the multiple fights, it is revealed there is another person above Dostoyevsky and that person must be stopped. During an encounter with one of Fyodor's allies, Sigma, Atsushi discovers that the leader of the Decay of Angels is a person who is codenamed Kamui. Ranpo Edogawa then manages to gather most of the Agency and prove their innocence to the law. After this, he uses his skills to determine Kamui's identity: Ōchi Fukuchi, the leader of the Hunting Dogs. Both Atsushi and Akutagawa are defeated by their enemy with the latter sacrificing himself in his last moments to let Atsushi escape. After the battle with Kamui, the next stage for the Decay of the Angel plan commences - turning people into vampires and eventually controlling humankind thanks to Bram. The United Nations decides to release One Order, an ability weapon that can make the listeners of orders given through the device act as ordered. The Agency fight the Hunting Dogs for their innocence and end the vampire reign. A young girl named Aya Koda takes Bram from Fukuchi to stop the vampires, eventually leading to Bram having a change of heart and betray Fukuchi. As Fukuzawa manages to defeat Fukuchi, he is revealed to have wanted to rid the world of wars through his methods and is killed by one his underling from the Hunting Dogs. Fyodor is defeated, leaving only an arm after crashing into the prison tower in a helicopter. However, it is revealed that his special ability is to take the body of whoever killed him, who in this case is Bram Stroker.