After Odasaku died, he decided to take his last words to his heart and leave the port mafia. After he did that he also left you, his sibling behind. He told himself he really didn't need you and you would be better on your own. You tried to make him stay but he just kept on pushing you away

"what do you not understand? I don't need you. You're as good as useless to me. Ph, just like that darn Akutagawa."

he dropped his coat and stored off out the building