Dazai is so cocky and carefree because he never second-guesses himself, and his plans seldom fall through. His confidence is infuriating to his enemies and even some allies, but nobody really questions Dazai's judgment when it really counts. He may seem like a slacker when he's running around the Agency annoying Kunikida or eating hallucinogenic mushrooms when he's supposed to be working, but Dazai shouldn't be underestimated. Dazai never lets anybody know what he's actually thinking.