Dazai

On the surface, Dazai is an irresponsible, insouciant detective. His intelligence is quickly revealed from behind his masquerade of stupidity, however. He is exceptionally intelligent and manipulative. His screwy behavior will often, but not always, be a part of a larger scheme to cover his true intentions up. Often, he enjoys playfully teasing or outright messing with others, such as Chuuya Nakahara and later Doppo Kunikida.

Truly, Dazai's closest friend was Sakunosuke Oda, a low-level mafia grunt whom he affectionately referred to as "Odasaku". Oda has come the closest anyone has come to fully understanding Dazai and the darkness that resides inside him. Because of this, Dazai held a deep loyalty to Oda, even after his death.

Dazai is revealed to have an exceptionally negative, potentially nihilistic, view of reality. He feels lonely and in the dark at all times. This gives him a detached side. Dazai will often switch between his playful, offbeat display and his stoic, pragmatic side. He also has no sense and very little interest in the concepts of good and evil. He only "redeemed" himself because of the wishes of his late friend, Oda, who encouraged him to be on the side that saves people.

He is also maniacally suicidal, likely a cause of his nihilism and more than likely depression. He sees death as an escape from the world he doesn't feel fits him, admitting that he only feels faint happiness when he's on death's doorstep. He's attempted suicide countless times, to the point where no one that knows him takes it seriously. His dream would be to commit double suicide (shinjū) with a beautiful woman.

He is almost maniacally homicidal at times. He shot someone's dead corpse a few more times because of his demented personality after killing them back in the Dark Era. He has also killed countless people and doesn't feel particularly remorseful because of it (at least not apparently). Dazai can also be very brutal, as demonstrated by his past mentorship of Ryūnosuke Akutagawa, where he berated and beat the latter frequently. Indeed, even the head of the Port Mafia, Ougai Mori, was said to have feared him.

His unique outlook results in him being exceptionally hard to understand. His true motives are almost impossible to figure out in any given situation, and he's generally very mysterious. This unreadability has given him an edge over his enemies in intriguing battles.

Despite all of this, Dazai is often the main source of comic relief in the series. His suicidal tendencies are usually played for comedy as is his clownish behavior.