The noodles in Japan were by far the best eats of the many meals during this first trip to Japan. I had pretty much written off udon and soba as somewhat boring and not-great texture and my first udon experience in Tokyo changed my mind. The concierge recommended a medium-sized noodle shop underneath the railway at the Yarakucho station. I have a business card that indicates they have a dozen or so locations but there's no english on the card so I can't tell you what the name of the shop is. It is located across the street from Fedex on the not-Ginza side of the station.
This was my first taste of cold udon dipped in a soy-based sauce with ginger and green onions. They have two sizes of noodles, on that is less thick and takes 6 minutes to cook and one that is thicker and takes 12 minutes to cook. I went with the thick noodles and it turned out that was a great choice. This dish is ultimately simple and allows you to enjoy the chewy texture of the noodle dipped in a simple yet tasty sauce. I also tried a bowl of the hot noodles, which was excellent as well. However, the texture of the noodles doesn't last since they continue to cook in the broth. Also, they only serve the thinner noodles during lunch.
This place could just be average since I don't have a lot of data points to compare to. I do know that I tried an udon place in Kyoto that the concierge recommended and it wasn't very good. For me this place was fantastic and was my top meal during the trip. I returned here for my last meal before heading to the airport.