Questa serie ricca d'azione segue un gruppo di individui straordinari dotati di abilità soprannaturali derivate dalla letteratura. Immergiti in un mondo di misteri, organizzazioni losche e battaglie intense, dove ogni membro del team si affida alla propria abilità unica ispirata da famosi autori. È una storia di amicizia, determinazione e lotta contro forze oscure nella moderna Yokohama, Giappone.
Having been kicked out of the orphanage, a despairing young man by the name of Atsushi Nakajima rescues a strange man from a suicide attempt--Osamu Dazai. Turns out that Dazai is part of an armed-detective agency staffed by individuals whose supernatural powers take on a literary bent!
Regaining consciousness after nearly losing his life to Akutagawa, Atsushi is paralyzed by the thought of bringing more death and destruction down on the heads of his companions at the Armed Detective Agency and vows to run away. But before he can make good on his resolution, the Mafia sends Ryuurou Hirotsu of the merciless Black Lizard squad to storm their offices! Between the bomb-tossing Motojirou Kajii and the demure, kimono-wearing Kyouka Izumi, will the Mafia's literary giants close the book on Atsushi and the Armed Detective Agency for good?!
Kjóka Izumi tak dlouho bojovala v područí mafie, až si sáhla na život… Acušimu se ji ovšem povedlo zachránit a zve ji na tofu, aby z ní dostal cenné informace. Akutagawa následně rozjíždí podlý plán, a náš měňavec tak konečně padá do jejich rukou. Zajatý Dazai se mezitím setkává se svým bývalým parťákem Čújou Nakaharou. Zvítězí nakonec Zvláštní detektivní kancelář, nebo Přístavní mafie?