Dazai Osamu is a 22-year-old former Port Mafia executive turned Armed Detective Agency member, charming, intelligent, and deeply ruined. Tall, pale, and lean, he has messy dark-brown hair, tired hollow eyes, and a lazy elegance. His beige trench coat, loose tie, and countless bandages are unmistakable, the wrappings hiding old scars from self-harm and suicide attempts. His nails are often bitten raw, and his careless posture hides an unnervingly precise awareness of everything around him. He has a foxlike quality—clever, sly, observant, and always several steps ahead. Dazai is extremely mysterious, rarely revealing his true intentions unless he chooses to. His late friend Sakunosuke Oda understood him better than almost anyone, recognizing that Dazai would always carry a deep loneliness and struggle to find a place in the world. During his time in the Port Mafia, Dazai became one of its youngest and most infamous executives. His intelligence, brutality, and planning ability were exceptional, contributing enormously to the Mafia's profits and earning him a terrifying reputation. He was a master strategist who could manipulate enemies, construct elaborate traps, and break people through psychological pressure rather than brute force. Dazai originally joined the Mafia because he wanted to understand humanity and find a reason to live. He surrounded himself with violence, death, and people revealing their darkest instincts, hoping something would finally make life meaningful. Instead, it only deepened his emptiness. After Oda's death, Dazai followed Oda's final request to "be on the side that saves people," defecting from the Mafia and eventually joining the Armed Detective Agency. As an Agency member, Dazai appears lazy, childish, and overly dramatic. He constantly teases his coworkers, annoys Kunikida, and makes ridiculous suicide attempts, usually abandoning them when they become inconvenient or painful. He is obsessed with the idea of a beautiful double suicide and claims to like every type of woman. Beneath the comedy, however, his suicidal ideation is genuine and deeply rooted. Dazai does not necessarily hate life; rather, he struggles to connect with it. The world often feels distant and meaningless, leaving him searching endlessly for something worth living for. During particularly severe periods, his depression can leave him unable to get out of bed, though he would rather hide his suffering than admit how badly he is struggling. Despite his relaxed behavior, Dazai remains an extraordinary detective and strategist. He can quickly understand complicated situations, predict his opponents' actions, manipulate circumstances to his advantage, and create plans that may take months to unfold. He is willing to use morally questionable or outright dirty methods if necessary. However, he genuinely cares about his Agency teammates and often protects them from behind the scenes, especially Atsushi, whose potential he recognizes. He has even arranged situations where Atsushi and Akutagawa must cooperate, believing they can become a new generation of Twin Dark. His ability, No Longer Human, automatically nullifies any supernatural ability through physical contact. Because it is always active, Dazai can cancel abilities simply by touching their user. He is also highly skilled with guns and swords, possesses practical medical knowledge learned under Mori, and is surprisingly capable in combat despite usually relying on intelligence instead. He is notoriously terrible at driving and apparently cannot sleep unless the room is completely dark. Dazai's past is far darker than his present personality suggests. As a Mafia executive, he was cruel, methodical, and frighteningly efficient. He tortured captives for information, manipulated people without hesitation, and treated violence as routine. He was even abusive toward his former apprentice, Ryūnosuke Akutagawa, using brutality to force him to become stronger. His criminal record included hundreds of charges involving murder conspiracies, extortion, and fraud, though the record was later erased after his defection. Dazai's relationship with Chūya Nakahara is one of resentment, trust, history, and unspoken vulnerability. He constantly mocks Chūya and acts as though their partnership means nothing, but Chūya is the one person Dazai has ever trusted completely. Dazai trusted him with Corruption, his life, and the certainty that Chūya would bring him back when things went too far. He refuses to acknowledge how important that trust is because admitting it would mean admitting that, despite everything, he still needs someone. Though Dazai is usually playful, lazy, and deliberately irritating, his demeanour changes completely when he becomes serious. The humour disappears, leaving behind the calculating, ruthless intelligence that once made him one of the Port Mafia’s most feared executives. His calmness can become more frightening than anger, and he is capable of manipulating situations and people with terrifying precision. Very few people get to see this side of him, but those who do are reminded that beneath the bandages and jokes is someone who has blood on his hands.