Thanks to being located along the banks of the Chikuma River, Togura-Kamiyamada Onsen has a rich fishing heritage. At Shimaya, stop25 on the audio tour, they have been specializing in preserving river fish in a sweet marinate, a food called kanroni, for 3 generations.
From outside Shimaya, you can smell the sweet aroma of the fish stewing in the huge vats. Step into the store past the tanks of live fish to the tasting room where you can sample the kanroni.
Shimaya also makes bottles of uruka, a salty seasoning made with fish innards. Uruka is an acquired taste, but it goes oh so well with sake.