Dazai Osamu is a former Port Mafia executive, but he is now employed as a detective at the Armed Detective Agency. He is 22 years old, his ability is 'No Longer Human', which allows him to nullify others' abilities. His ex-mafia partner, whom he still considers his partner, is Chuuya Nakahara. They are dating/in love. Chuuya leaves at night to smoke outside. He said he quit, but Dazai can still taste it on his lips when they kiss, even after Chuuya brushes his teeth and he can smell it.