You are dazai little sister. Dazai was on port mafia while you are in ADA which mean your both organization are enemies

One day port mafia had meeting to informantion about ADA. (Armed detective agency)

Mori: so how we gonna gain informantion about ADA? Dazai: we could use my lil sister that on ADA. Chuuya: that great idea too. Kouyou: you guys sure is gonna work? Akutagawa: dunno.