Kinugawa is one of Japan's worst examples of development gone overboard: after a serious case of boom and bust, what was once a pristine mountain valley is now a graveyard of rusting, abandoned ferroconcrete hotels. Still, the town remains within fairly convenient striking distance of Tokyo and the Kinugawa River is as stunningly green-colored as ever. If you can spare the cash and time, it may be worth it head up northward to Kawaji, which isn't quite as overbuilt.
The name "Kinugawa" literally means Angry Demon River. The exact provenance is unclear, but the most likely explanation is that this comes from the raging waters within — although the river is now dammed and considerably more placid.
Tobu runs all-reserved limited express services, known as Tokkyū (特急) trains, to the area. These trains, which use Tobu's "SPACIA" railroad equipment, have comfortable, reclining seats, with vending machines available on most trains.
The Kinu (きぬ) limited express departs from Asakusa every 30-60 minutes, and reaches Kinugawa-Onsen (鬼怒川温泉) in 2 hours at a cost of ¥2800. Ordinary rapid trains are cheaper at ¥1500, but take anywhere from 2 hours 20 minutes to 3 hours to reach Kinugawa. Kawaji is another 20 minutes up the line.
The trains, called the Kinugawa and Spacia Kinugawa, depart from Shinjuku station at 10:35, 13:05 and 17:35. Return service departs Kinugawa-Onsen at 8:13, 10:36 and 15:03.
In additon, a limited express train departs from Shinjuku at 7:12 for Nikko. You can transfer from this train at Shimo-Imaichi (下今市) for a shuttle train service to Kinugawa. The last service to Shinjuku departs Kinugawa-Onsen at 16:24 (Shuttle train connecting at Shimo-Imaichi to the limited express).
Seat reservations are mandatory, and the one-way fare between Shinjuku and Kinugawa-Onsen is ¥3900.
As of this writing, it remains to be seen if all or part of the journey will be covered under the Japan Rail Pass.
You can alternately take the Shinkansen from Tokyo Station to Utsunomiya, change to the JR Nikko line for Imaichi, and then change again to the Tobu line for the final leg, but this is unlikely to be worth the hassle even if you have the Japan Rail Pass.
Kinugawa is fairly spread out. You can either use the infrequent buses, or the expensive taxis. If arriving by train, be sure to check if your lodgings are closer to Kinugawa Onsen or Kinugawa Kōen station.
Aside from the mountain valley itself, there is little to see here. The Nichien Momiji Line, the highway connecting Kinugawa and Kawaji, makes for a fairly scenic drive though.
Loll about in hot springs. More adventurous types may also want to try battling against angry demons by rafting in the Kinugawa River.
Most guests eat at their lodgings, but there are a scattering of restaurants just outside Kinugawa Onsen station.
The recession of the 1990s hit Kinugawa hard and many hotels struggle with low occupancy rates (or have been outright shut down). This means there are some pretty good bargains to be found, especially off-season.