Soba
Some establishments, especially cheaper and more casual ones, may serve both soba and udon (thick wheat noodles) as they are often served in a similar manner. However, soba is traditionally the noodle of choice for Tokyoites. This tradition originates from the Edo period. At that time, the population of Edo (Tokyo) was much richer than the rural poor, were more susceptible to beriberi because of  their high consumption of white rice which is low in thiamine. They are thought to have made up for this by regularly eating thiamine-rich soba. Every neighbourhood had one or two soba establishments, many also serving sake, which functioned much like modern cafes where locals would drop by casually.