そうめん (soumen) are very thin noodles made of wheat flour and are usually served cold with a light flavored dipping sauce, つゆ (tsuyu). The tsuyu is usually a katsuobushi-based (bonito flakes) sauce that can be flavored with finely chopped spring onion, wasabi, ginger, or myoga (Zingiber mioga). In the summer, soumen chilled with ice is a popular meal to help stay cool.
Some restaurants offer ながしそうめん (nagashi-soumen , flowing soumen noodles) in the summer. The noodles are placed in a long flume of bamboo across the length of the restaurant. The flume carries clear, ice-cold water. As the soumen pass by, diners pluck them out with their chopsticks and dip them in tsuyu. Catching the noodles requires a fair amount of dexterity, but the noodles that are not caught by the time they get to the end usually are not eaten, so diners are pressured to catch as much as they can. A few luxury establishments put their soumen in real streams so that diners can enjoy their meal in a beautiful garden setting. Machines have been designed to simulate this experience at home.
(Story based on the article at: https://en.wikipedia.org/wiki/S%C5%8Dmen)
