Kamaage udon is a type of udon noodles which are soaked inside the hot water which was used to boil the noodles. The noodles and the water are placed inside a wooden tub or bowl and eaten with a lukewarm soy sauce based dipping sauce. Therefore, do not put the sauce into the tub!
Normally udon noodles are boiled and then washed by cold water to remove the sliminess but kamaage udon noodles are not washed by cold water at all. Therefore, the mouthfeel will be different then ordinary udon. Then, due to served with dipping sauce, kamaage noodles can be shared easily than other type of warm udon noodles. There are kamaage noodles for two or more, family size too.
Kamaage udon is mostly offered at diners specialized in udon. It is a popular menu at udon diners which are specialized in Sanuki style udon. By the way, Sanuki is a former province in Shikoku, which is currently called Kagawa prefecture.