Udon is different between west and east Japan. The noodle is almost the same but the soup is different. The taste and the color of the soup in the Kanto region, which includes Tokyo, are stronger and richer, respectively. In the Kansai area that includes Kyoto, the flavor is lighter and the soup is thinner. Many Kansai people are surprised when they see the brown tsuyu in Kanto, because in Kansai its pale color is clear. There are three different causes: soy sauce, stock, and water.