This is a map showing the area around Yasaka-jinja, which is the square in blue on its own at the top of the map. The houses in green are part of Housenji-ku (ku = community ward) and the houses in blue are part of Tenno-ku. As you can see, there isn't exactly a neat dividing line between them... I asked around to find out the reason for this, and it seems that it's mostly down to the division of rice fields - most of the families own a rice paddy, but the division of them is akin to medieval strip farming, with hundreds of narrow fields joined together like a giant agricultural jigsaw puzzle. This method of farming is part of the reason why Japanese rice is so expensive, and why the government has to spend millions and millions of yen each year subsidising inefficient, small-scale farmers. Having said that, it would be sad to see this kind of close-knit farming community disappear for the sake of efficiency and cheap rice...