Inaniwa is one of Japan's classic udon styles: thin, smooth, hand-stretched noodles from the old Inaniwa village area of Yuzawa. Sato Yosuke's flagship store is the easiest place for travellers to understand why it matters, because it combines a restaurant, shop, and visible production area.
The factory viewing is short, but useful. You see the kneading, twisting, stretching, and drying that give the noodles their texture, then sit down and taste them properly. It is a modest stop, but it anchors Yuzawa in something more specific than scenery alone.