In Nasu resort area, there are many gourmet restaurants. Comparatively we have more Soba and Udon noodle restrautants and Western style restaurants than what we usually see in Urban cities like Ramen, Chinese, Tonkatsu, or some fast food places.
Udon is a Japanese traditioanl noodle besides Soba noodle. Many of the traditional Udon are like just Udon only with small stuff like Age ( fried Tofu), leek, or egg on the Udon noodle Tempura on the Udon is recently a standard style but it was rather a delux Udon dish and we could have it just on special occassion when I was a kid becuase tempura Udon costs more.
Recently in Japan, hard and thick texture Udon called Sanuki Udon ( traditional type in Shikoku island of Japan ) is really popular, and it's chain shop called Marugame Udon restautants are also expanding both in Japan and in some of other countries. I hear it's really popular in Hawaii too.
In Nasu, there is a newly sophisticated Udon dish. At Okamoto Udon restaurant, we can have a carefully made modern Udon dish ( as photo). It's cold Udon with delicately blended soy source dashi soup which we put on the Udon by ourselves, as the photo below, it comes with no soup fristly, then we do it by ourselves. The taste is fabulous. Noodle is not so hard but good enough to enjoy resilient texture. Tempura is also softly cooked, we don't feel like heavy oily food because the oil is quite lightly ( not heavily ) used in Tempura making. The balance of Udon Noodle and Tempura is really good.
AS a problem, the location might be hard to find. Please contact me if you really wish to go here. I think I can show you the route to this place and some more info.