Yokohama (ヨコハマ, Yokohama?) is the primary setting of the events.
It is a port city with a mixture of modern buildings and nostalgic buildings, but since the end of the war, allied-affiliated warlords have flown in and have built up an autonomous region by shaking extraterritorial powers. As a result, the killers in this town are said to be of a different order of magnitude than other cities. There are various dark organizations and foreign illegal capital, with the port mafia being said to take root in all parts of the town's politics and economy.
It is also said that a "book" has been sealed somewhere in the city.
- Although the real Yokohama's name is written in kanji, in Bungo Stray Dogs the katakana form is used.