The Port Mafia (ポートマフィア, Pōto Mafia?) is an underground criminal organization run by Ōgai Mori, based in Yokohama, Japan. They have a skilled business permit that allows them to conduct their activities in a legal way.[3] They are also known as Yokohama's "Night Wardens".

Dazai is a mysterious person, his true intentions are never revealed unless he reveals them. The person who got closest to the truth of his personality, as acknowledged by Dazai himself, was his friend Sakunosuke Oda. 