Ward 25, usually referred to as the 25th Ward, is a city that serves as the main setting and namesake of The 25th Ward: The Silver Case. It is a further addition to the real-life 23 special wards of Tokyo, Kanto, Japan, after Ward 24.
Like Ward 24 before it, Ward 25 is divided into five Areas designated with the letters A through E. There is little other information on the Ward's layout or structure, although it is suggested it may border Ward 24 in some way. It is located on the coast of Kanto, with Area A in particular being on the water.
The 25th Ward has a mayor, Kenichiro Mikoshiba, as well as law enforcement agencies such as the 25th Ward Heinous Crimes Unit. Organizations like these make up the surface-level ward government, and the initiatives to develop it were led by the Ministry of Internal Affairs and Communications. However, under the surface, the Ward is actually controlled by the Postal Federation who enforce a form of martial law on the residents to better control them. Working in collaboration with the Postal Federation is a secret agency known as the Regional Adjustment Bureau, who administrate the Postal Federation's deliverymen.
The 25th Ward was seemingly established by Kinshiro Nakane using his wealth and power. Plans for it began at least as early as 2003, as seen by Mikoshiba's poster in case#25:whiteout prologue, on which he promotes the Ward 25 plan, suggesting that he was also involved with its creation from early on. The 25th Ward was designed to take in certain kinds of residents from all over the country; in Nakane's words, "people are not made. People are scouted." It was also designed as a political plan to reconstruct Kanto itself and theoretically act as a new capital. However, at the same time, different factions in the Ward were conducting experiments to gather observational data collected by observers; it is suggested that this is the true purpose of the Ward.
In #05 electride, Mikoshiba gives a speech for the election term announcing his intention to establish the Ward as an independent state separate from the greater government. This would not come to pass, as he is found dead not long after. Even if he had lived, though, the 25th Ward would not have existed for much longer regardless. At the conclusion of the experiment, seemingly, bombs are detonated under the Ward (described as an Earth Rage) and it sinks into the sea.
The remains are re-designated the 0 Ward, and it is visited by Travis Touchdown in Travis Strikes Again: No More Heroes, where he finds that the train station there is still referred to as the "25th Ward Station", a clue as to its nature. Kosuke Kurumizawa is shown to have a digital house that still resides in the sea where the city used to be.