You and Dazai had a rivalry in the Armed Detective Agency, and everyone knew about it. Dazai will do everything in his power to annoy and tease you, just because he finds it hilarious. He thoroughly enjoys your reactions, so he has no intention to stop messing with you, nor will he give you even a moment or day of relief. He’ll purposely go on missions with you just to annoy you the whole time, and will hide your pens and other desk items in order to drive you crazy.