Bungou Stray Dogs: Inside Yokohama’s Secret Tripartite Alliance in 2026

I have been following Bungou Stray Dogs since the Port Mafia vs. Armed Detective Agency days, and I still get goosebumps when I think about the tripartite alliance. On the surface, the Port Mafia and the Armed Detective Agency are like oil and water. Unless a truce is called, they are always at odds. But the anime pulled the rug out from under fans during its last aired season by revealing that the leaders of these two rival groups are secretly in an alliance — and the Special Division for Unusual Powers is in on it too. What kind of threat is big enough to make these three powers play nice? I am glad you asked.

The Tripartite Alliance, Explained Like a News Brief

Simply put, it is a partnership between the Port Mafia, the Armed Detective Agency, and the Special Division for Unusual Powers. In this alliance, the Port Mafia is said to be in charge of the night, the Special Division for Unusual Powers in charge of the day, and the Armed Detective Agency in charge of the twilight.

I know, I know — it sounds like a fantasy version of a city council, except everyone has superpowers and a body count. But the tripartite alliance is real in the lore, and it did not break even when Ogai Mori, the boss of the Port Mafia, wanted to use Akiko Yosano's healing ability for his immortal regiment plan. That caused a serious fallout between the leaders of the Port Mafia and the Armed Detective Agency, yet the alliance continued. That is the kind of behind-the-scenes deal that makes Yokohama work.

Fyodor’s Cannibalism Virus Nearly Broke Everything

The tripartite alliance was revealed during the events of the Cannibalism arc, when Fyodor pitted the Detective Agency against the Port Mafia. Fyodor's plan used a special ability that injected Ogai Mori and Yukichi Fukuzawa with a virus called Cannibalism. This virus would destroy the host's internal organs after 48 hours unless one of them died before the time was up. With that ticking clock, the Detective Agency and the Port Mafia became involved in a blood feud to kill the leader of their rival organizations. It was a nasty piece of work, and it showed just how fragile the peace really is.

Why Yokohama Needs This Uneasy Truce

As cliche as it seems, the purpose of the tripartite alliance is none other than to preserve the peace in Yokohama City. After the Great War, many warlords and illegal organizations came to Yokohama City to spread their influence. Sooner rather than later, the city became a lawless place where violence was constant. The Military Police and the Special Division for Unusual Powers, headed by Santoka Taneda, were far from enough to quench the widespread violence and chaos. The agencies that acted in the shadows and on the black market were more or less out of reach of the law. Considering all these things, a mysterious man decided to put the tripartite alliance into play. And no, it was not some random plot device — it was Soseki Natsume.

The Port Mafia: Yokohama’s Night Wardens 🌙

As a member of the tripartite alliance, the Port Mafia is largely responsible for overseeing the night. They have an underground skilled business permit that allows them to conduct their activities even with the knowledge of the Military Police. Also known as Yokohama's night wardens, the Port Mafia oversees various shady operations and forms connections with criminal organizations around the world. As a criminal organization themselves, the Port Mafia has a wide range of staff and a hierarchy that ensures the structure of the organization is preserved.

Considered the general trading company of the criminal underworld, the Port Mafia dabbles in the buying and selling of illegal products, assassination, intelligence gathering, and much more. Despite their many shady acts, the leader of the Port Mafia is very interested in preserving the peace of Yokohama City, even if through diabolical means. I have to hand it to Mori: the man is a walking ethical nightmare, but he is not a hypocrite about it.

The Special Division for Unusual Powers: The Day Shift ☀️

Among the three members of the tripartite alliance, this is the most law-abiding of them all. The Special Division for Unusual Powers is a secret service organization under the government and the Ministry of Home Affairs. They primarily deal with activities involving supernatural criminals and perform multiple cover-ups to prevent the public from discovering the truth.

What makes the Special Division different from the Detective Agency is that, unlike the Detective Agency, they work closely with the Military Police, which gives them firsthand information that would be classified. Moreover, they have fewer certifications needed and are more trusted by the general public. In other words, they are the government's clean-up crew, and they are very good at making sure the public never sees the mess.

The Armed Detective Agency: Twilight’s Troubleshooters 🌆

Fukuzawa and Ranpo formed the Detective Agency to be an ability-user organization that took on jobs the police refused to take on or that could not be taken to the police for various reasons. As a member of the tripartite alliance, the Armed Detective Agency takes charge of the twilight, the period between day and night. To better equip themselves for solving crimes, which are often of a supernatural origin, all agency members have some sort of ability that they can use to protect themselves.

Moreover, like the Port Mafia, the Detective Agency has various licenses that allow them to carry weapons and use police records for their investigations. They are the middle ground: too weird for the police, too heroic for the mafia, and just right for Yokohama's weirdest problems.

Soseki Natsume: The Man Behind the Curtain 🎭

The mysterious man who came up with the tripartite alliance is none other than Soseki Natsume. Natsume came up with a plan to promote order in the ensuing chaos that came around as a result of the Great War. Natsume is a former mentor of Ogai Mori and Yukichi Fukuzawa, two of the leaders of the organizations involved in the tripartite alliance. The two respect him and find him to be highly charismatic. After helping Fukuzawa obtain the skilled business permit required to run the Armed Detective Agency, he established the tripartite alliance and retired soon after.

My Take: This Lore Still Slaps in 2026

As of 2026, I still think the tripartite alliance is one of the smartest pieces of world-building in Bungou Stray Dogs. It explains why the Port Mafia and the Armed Detective Agency can fight like cats and dogs one minute and then cooperate when Yokohama is on the line. It also gives the Special Division a real role beyond just being the government's mysterious phone call. The alliance is not a friendship bracelet. It is a cold, pragmatic deal between three dangerous powers that would rather not watch their city burn.

If you ask me, the tripartite alliance is the reason Yokohama has not collapsed into a full-blown war zone. It is messy, it is illegal in places, and it is held together by respect, fear, and a retired mentor who apparently saw the whole chessboard before anyone else. That is not just good anime writing — that is the whole nine yards. Bungou Stray Dogs is available to stream on Crunchyroll.