Japanese noodles

Udon noodles

Udon is a type of thick wheat-flour noodle popular in Japanese cuisine.
Udon is usually served hot as noodle soup in a mildly flavoured broth, in its simplest form as kake udon, served in kakejiru made of dashi, soy sauce (shōyu), and mirin. It is usually topped with thinly chopped scallions. Other common toppings include tempura, often prawn or kakiage (a type of mixed tempura fritter), or abura age, a type of deep-fried tofu pockets seasoned with sugar, mirin, and soy sauce. A thin slice of kamaboko, a halfmoon-shaped fish cake, is often added. Shichimi can be added to taste.
The flavor of broth and topping vary from region to region. Usually, dark brown broth, made from dark soy sauce (koikuchi shōyu) is used in eastern Japan, and light brown broth, made from light soy sauce (usukuchi shōyu) is used in western Japan. This is even noticeable in packaged instant noodles, which are often sold in two different versions for east and west.

The origin of udon in Japan is usually credited to Kūkai. Kūkai, a Buddhist priest, traveled to China around the beginning of the 9th century to study Buddhism. When he returned, he also brought back the knowledge of udon soup to his farmer neighbors in the Sanuki region of Japan. In China, similar thick wheat flour noodles are called cū miàn. This original udon was 2 to 3 cm in diameter, a flat pancake-shaped "noodle" added to miso-based soup. In modern Chinese, the characters 餛飩 refer to wonton dumplings, not noodles. (Compare pasta, which can be both noodle-like and dumpling-like.) The noodles are called wūdōng or wūdōngmiàn, sometimes wūlóngmiàn. (Note that this is unrelated to Oolong tea, wūlóngchá.)
___________________________________________________________________ Soba noodles

Soba is a type of thin Japanese noodle made from buckwheat flour. It is served either chilled with a dipping sauce, or in hot broth as a noodle soup. Moreover, it is common in Japan to refer to any thin noodle as soba in contrast to udon which are thick noodles made from wheat. It takes three months for buckwheat to be ready for harvest, so people can harvest it four times in a year; it is harvested mainly in spring, summer, and autumn. In Japan, buckwheat is produced mainly in Hokkaido. People call soba that is made with buckwheat that has just been harvested "shin-soba". It has more flavor, sweetness and taste than soba.

In Japan, soba noodles are served in a variety of situations. They are a popular inexpensive fast food at train stations throughout Japan, and are served by exclusive and expensive specialty restaurants. source of info from wikipedia.