Route Name: Natsukoya-sawa (夏小屋沢)
Location: Matsuki-sawa valley (松木沢)
Map sheet: 13 [Yama-to-kougen-chizu (山と高原地図) series]
Time: 1 day
Grade: WI4 / Overall grade 2+ alpine route
The Matsuki-sawa valley, near the old copper mining centre of Ashio, is not only a beautiful and remote location with a fascinating recent history, but is home to a handful of the best frozen sawa ice climbs in the Tokyo area. The Kuro-sawa gully is probably the most popular classic in the area, but its immediate neighbour Natsukoya-sawa is a little harder and slightly more sustained, packing 7 icefalls into the same approximate route length.
Mid-February usually offers the best conditions here, and whether you choose a one-day climb or a full weekend combining it with one of the neighbouring routes, you are unlikely to be disappointed with this excellent outing.
If travelling from Tokyo (東京) by car, take the Tōhoku Expressway as far as Utsunomiya (宇都宮), then change onto the Nikko-Utsunomiya road until it turns into Route 120. Turn left onto Route 122 and stay on this until it meets Route 250, then turn right onto Route 250. Keep going straight on up the Ashio (足尾) valley on this road until you reach its end at the small car park above the Akagane Water Park (銅親水公園).
From the car park, you need to walk a little further up the road you drove in on, go past the barrier blocking the road, and cross the bridge to get over the river on the left. Walk along the road as it doubles back round to the left and then swings northwest again towards the entrance to Matsuki-sawa (松木沢). Once into Matsuki-sawa you need to keep walking for about 1.5 hours until you reach the entrance to Kuro-sawa (黒沢). Initially you will be on a good dirt road until you arrive at the Matsuki village.
From there onwards the road becomes less maintained, and in several places has been completely covered in boulders from landslides and rockfall from the mountainside on your right.
On the left side of the valley large rock faces begin to appear, and the summit ridge of Nakakura-yama (中倉山) can be seen high above. This ridgeline eventually leads over Koushin-san (庚申山) to Nokogiri-yama (鋸山) on the main ridge before the summit of Sukai-san (皇海山), and is a dramatic and high-quality hike in its own right.
Eventually you will arrive at a large concrete dam next to the Kuro-sawa valley coming down the mountainside on your left. Continue past the dam for a short way and then drop down to the river. Cross the river by whatever means you find easiest, and then walk upstream along the left bank. Natsukoya-sawa is the second sawa entrance that you will meet.
You will be rappelling down and back out the same way, so leave any gear that you don’t want to carry up the route here at the entrance.
F1 and F2 are fairly short and not too steep, easily soloed. They provide a nice warm-up for the climbing above.
After about 80m you will arrive at the crux F3 icefall. It is about 20m high and vertical, and depending on conditions, it can be quite chandeliery and serious for its relatively short stature. There are trees to anchor from just above it.
Now continue a short way around an S-shaped bend in the sawa, and climb F4 via its two steps, each about 8m in height. As usual for this route, you can anchor to a solid tree beyond the top.
The next pitch continues up the stream bed and around a corner where it hits F5, a superb narrow 20m runnel with rock walls on either side, with a tree anchor at the top.
F6 is quite gentle and follows a broader section of the stream up for about 40m with no real difficulty until the bottom of F7.
F7 is a short-lived but plumb vertical icefall of about 8-10m. Above F7 the gully continues, but the ice is finished and there’s no real reason to continue.
To get back down, simply rappel off the tree anchors at the top of each icefall (in-situ cord on most, but consider replacing it with your own if unsure). A doubled-over strand of 60m rope should be long enough to get you down any individual rappel.
An excellent route in a beautiful setting, much more akin to alpine climbing than to single-pitch ice cragging. Climb it in a one-day hit, or make a weekend of it by combining it with one of the neighbouring routes.
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