The Tokyo area is considered the most populous metropolitan area in the world . This does not mean that only consider the people living in Tokyo, if not the number of people moving through Tokyo daily, so this includes many people from the cities of Kawasaki, Chiba and Saitama around Tokyo, and which come daily to Tokyo to work, doing so Tokyo is the most populated urban area in the world (Tokyo really "only" has 12,527,115 inhabitants).
Unlike as often happens in Spain, in the Tokyo area and surrounding cities, there is no separation between one city to another, so while crossing a street, we have entered another city, this makes all looks like a single city.
While all this as one city, living in Tokyo or do events in Tokyo rather than in cities next door has more prestige. If you went to look for a flat in Tokyo, you will see that there are areas that only a few blocks to go further and be considered as Saitama, Chiba and Kawasaki, floor prices drop considerably.
Another good example of this is to put the name of Tokyo to the events you want to have a great success, such as the famous example of the Tokyo Game Show, which is not otherwise in Tokyo in Chiba, and Tokyo Disneyland also is in Chiba, but we all know that Tokyo Game Show sold more than Chiba Game Show and just this a few stations in Tokyo, so many people when these events will not know that part of Japan and Tokyo if not Chiba not.
When you purchase a map of Tokyo trains, as normal is that this map encompassing these 4 cities.
Image of Chiba bank . (Kawasaki is a city in Kanagawa Prefecture)
