Osamu Dazai

Dazai presents himself as lazy, whimsical, irritating, and preoccupied with finding a painless way to die. He regularly abandons Kunikida during work, gives absurd explanations with a straight face, and asks attractive women to join him in double suicide. His eccentric behavior makes it difficult even for colleagues to determine when he is being sincere.

Beneath that performance, Dazai is exceptionally calculating. He can infer another person's motives from small behavioral details, predict how multiple factions will react to a crisis, and construct plans whose real purpose may remain hidden from his own allies until the final stage. He is willing to deceive friends when he believes withholding information increases their chances of success.

Dazai has a bleak understanding of human nature. His fascination with death is not merely an occasional joke; it reflects a longstanding detachment from ordinary ideas of purpose and fulfillment. Nevertheless, he repeatedly acts to save people and preserve the Agency, even while refusing to present himself as heroic.

His treatment of younger ability users reveals a complicated mentorship style. Dazai rarely offers straightforward reassurance. Instead, he creates situations that force Atsushi and others to make their own choices, sometimes with considerable emotional or physical risk.

Dazai's ability, No Longer Human, nullifies supernatural abilities whenever he physically touches their user or manifestation. The effect activates automatically, meaning he cannot simply choose to let an ability affect him while contact is maintained.

This makes him particularly dangerous against opponents who depend heavily on supernatural power. Transformations can be cancelled, ability-created phenomena can be neutralized under the appropriate circumstances, and even extraordinarily powerful gifts become useless when Dazai reaches their user.

No Longer Human also creates unusual interactions with healing abilities because ability-based treatment cannot normally operate on Dazai while his nullification is active. His colleagues therefore have to account for this property when he is seriously injured.

Dazai's greatest weapon, however, is his intelligence. He is an expert planner, interrogator, manipulator, and observer who regularly anticipates events several moves in advance. He understands both the Armed Detective Agency and Port Mafia well enough to exploit the strengths, habits, and political interests of each organization.

He is also a capable fighter despite lacking a physically offensive ability. Dazai uses hand-to-hand combat, firearms when necessary, traps, psychological manipulation, and environmental advantages rather than trying to overpower stronger opponents directly.

His former partnership with Chuya Nakahara demonstrates one of No Longer Human's most strategically important applications. Dazai can stop Chūya's Corruption state by touching him, allowing Chūya to use an otherwise uncontrollable level of power without being consumed by it.

Dazai first appears when Atsushi pulls him from a river during one of his attempted suicides. Along with Kunikida, he is investigating a tiger that has been appearing around Yokohama. His investigation leads him to identify Atsushi as the ability user responsible and to neutralize the transformation.

Dazai arranges circumstances that bring Atsushi into the Armed Detective Agency, establishing himself as a mentor whose methods are rarely transparent. He soon becomes instrumental in countering the Port Mafia's attempts to capture Atsushi.

His familiarity with the Mafia quickly suggests that his knowledge extends far beyond normal detective work. Dazai was formerly a Port Mafia executive and became the youngest executive in the organization's history. During that period, he operated directly under Mori and formed the feared Double Black partnership with Chūya.

Dazai's earlier life is explored extensively through the Dark Era. His friendship with Sakunosuke Oda becomes the decisive influence behind his eventual departure from the Port Mafia. Oda's dying request that Dazai choose the side that saves people leads him toward the Armed Detective Agency.

During the Guild conflict, Dazai works largely at the strategic level, coordinating responses to threats that neither the Agency nor Port Mafia can handle independently. His understanding of both organizations makes him a natural intermediary when Yokohama itself is endangered.

Later conflicts pit Dazai against Fyodor Dostoevsky, an opponent whose intelligence can match his own. Their battles increasingly resemble contests of prediction and information rather than straightforward fights. The Decay of the Angel crisis eventually places Dazai in circumstances where he must continue opposing Fyodor while physically separated from most of the Agency.

Atsushi Nakajima is Dazai's junior colleague and protégé. Atsushi Nakajima frequently depends on Dazai's guidance, while Dazai deliberately pushes him toward independent decisions rather than allowing him to remain dependent.

Doppo Kunikida is Dazai's principal Agency partner. Dazai constantly sabotages Doppo Kunikida's schedules and exploits his gullibility for amusement, but he respects Kunikida's ability and trusts him with serious operations.

Chuya Nakahara is Dazai's former Port Mafia partner and enduring rival. Dazai and Chuya Nakahara openly insult each other, but their former Double Black partnership rests on exceptional combat synchronization and deep knowledge of each other's capabilities.

Ryunosuke Akutagawa was Dazai's subordinate in the Port Mafia. Dazai trained Ryunosuke Akutagawa harshly and withheld the approval he desperately wanted, leaving Akutagawa obsessed with proving himself worthy even after Dazai left the organization.

Sakunosuke Oda was one of Dazai's closest friends during his Mafia years. Sakunosuke Oda's moral outlook reaches Dazai in a way few others can, and his final advice becomes the central reason Dazai leaves the Mafia and chooses to save people instead.

Ango Sakaguchi completed the trio of friends who regularly met at Bar Lupin. Dazai's relationship with Ango Sakaguchi becomes complicated by Ango's role as a government operative infiltrating the Mafia and the events surrounding Mimic.

Ogai Mori was Dazai's superior in the Port Mafia. Dazai understands Ogai Mori's ruthless utilitarian thinking extremely well, while Mori recognizes Dazai as both a valuable strategist and a potentially dangerous adversary.

Fyodor Dostoevsky is Dazai's most prominent intellectual opponent. Fyodor Dostoevsky can anticipate strategies at a level that forces Dazai to rely on elaborate contingencies, coded communication, and knowledge of his allies.

Kyusaku Yumeno, or Q, has a particularly hostile history with Dazai. Dazai's nullification makes him one of the few people capable of reliably stopping Kyusaku Yumeno's dangerous ability.