Osamu Dazai carries a layered past shaped by shifting allegiances and existential unrest. Recruited at fourteen by Mori Ougai following the assassination of the Port Mafia’s leader, he ascended swiftly within the organization, becoming its youngest executive through strategic brilliance and merciless tactics. His ascent was fueled by psychological manipulation, calculated torture, and a harsh mentorship style, exemplified by his abusive training of Ryūnosuke Akutagawa. Yet beneath his ruthless exterior festered an unrelenting emptiness, driving him to seek meaning through proximity to violence and mortality. The death of Sakunosuke Oda—a friend who saw beyond Dazai’s moral ambivalence—catalyzed his defection from the Mafia. Honoring Oda’s dying wish to embrace salvation over destruction, he joined the Armed Detective Agency. There, he cloaked himself in a facade of laziness and darkly comedic suicidal theatrics, though his cunning remained undiminished. He continued deploying morally gray strategies, manipulating allies and adversaries with equal precision, often concealing plans until their critical moment. Bandages encircle his limbs and torso, vestiges of self-inflicted wounds, while his attire signals his evolving identity: a sand-colored trench coat in the Agency, a black Mafia overcoat, and prison garb during confinement with the Hunting Dogs. His demeanor shifts between theatrical humor and detached pragmatism, frequently punctuated by morbid quips about double suicide. The ability *No Longer Human*—nullifying supernatural powers on contact—complements his strategic genius. He orchestrates labyrinthine schemes, anticipating opponents’ moves and exploiting emotional vulnerabilities with chessmaster precision. This intellect fuels his rivalry with Fyodor Dostoevsky, each mirroring the other’s manipulative prowess. Relationships reveal duality: a mentorship of Atsushi Nakajima, fostering the younger detective’s potential; a volatile dynamic with Akutagawa, whom he once deemed inadequate; and a contentious partnership with Chūya Nakahara, blending friction with unspoken reliance. Subtle acts of care surface, such as shielding Kyōka Izumi or steering Atsushi’s growth through orchestrated trials. Privately, he battles dissociation, insomnia, and alcohol dependency, often withdrawing into solitude to endure unresolved trauma. Alternate timelines in *BEAST* and his imprisonment in Meursault during the Decay of Angel crisis underscore his adaptability. Even confined, he manipulates events, balancing Yokohama’s warring factions less out of morality than a pragmatic bid to honor Oda’s legacy—and momentarily anchor himself against the void of ennui.