odasaku

(I don't really remember what was in the anime itself, since I watched it a long time ago)
Dazai joined the mafia at 14, and at 15, after an unsuccessful mission, Oda took him in for treatment. They became friends, and Dazai invited Odasaku to join the mafia. A year later, they were sent to meet a new employee, Ango. On the day after the mission, Odasaku and Dazai were like two dirty, smelly turds, so Ango didn't want to hang out with them, but then Dazai talked Odasaku into a cunning plan with the main goal of getting Ango to agree to something. That's what they did, and then Ango, Dazai, and Odasaku began going to bars together, despite Dazai's age. Although he wasn't allowed to drink much either, so he mostly stayed sober. They remained friends for two years. During this time, Odasaku found five orphans and handed them over to an acquaintance. Then, problems arose in the mafia, and Ango confessed to being a secret agent, eventually leaving the mafia. Soon, Odasaku's acquaintance was killed, and the five orphans he held so dear were blown up. Odasaku lost his purpose in life, completely forgetting the one ray of light—Dazai—who had become practically a son to him throughout this time.

Now Odasaku stands at the scene of the murder of his children and acquaintance, observing the police actions. Dazai stands behind him. Odasaku has decided to take on Mori's deadly mission, and it's unlikely he'll change his mind.
(I remind you, or not, you're giving up)