Route name: Daidoushin-sawa Ōtaki (大同心沢大滝)
Mountain: Yatsugatake (八ヶ岳)
Map sheet: 32 [Yama-to-kougen-chizu (山と高原地図) series]
Time: 2-3 hours
Difficulty: WI4+ icefall
The Daidoushin-sawa Ōtaki (大同心沢大滝) is a stunning frozen waterfall that makes up the centre-piece of the Daidoushin-sawa gully in the Akadake-kōsen area of Yatsugatake. At 50m high it is the tallest icefall in the surrounding area, making it visible on the hike up to the Akadake-kōsen hut.
If travelling from Tokyo, take a Super Azusa Limited Express train from Shinjuku to Chino (approx. 2.5 hours). Outside the JR station at Chino take a bus to Minotoguchi (美濃戸口, approx. 45 minutes). This is the gateway to the Akadake-kōsen side of Yatsugatake. From the carpark start hiking up the trail that is signposted to Akadake (赤岳). The walk-in takes up to 3 hours by map time. It is split into 3 stages. The first hour brings you past a series of buildings and on a little further to a hut with a water source, which makes a good resting point for 5 minutes. The trail splits here, with the right fork going up Minami-sawa (南沢) to the Gyouja-goya hut (行者小屋). You need to take the left fork up Kita-sawa (北沢). The next hour follows the rough dirt road until it finishes at a bridge across the sawa. From the other side the path narrows and meanders alongside the sawa for another hour or so until you reach the hut at Akadake-kōsen. This hut and its campground serve as basecamp for all the routes in the area.
As you exit the Akadake-kōsen hut by the front door, take the steps opposite the hut to gain the trail that provides access to the ice routes (Daidoushin-sawa, Uradoushin runze, Jōgosawa) on the left-hand side of the face below the summit of Yokodake (横岳).
Follow the trail for about 15 minutes through the forest and you will come to a signpost pointing right into the bottom of the Daidoushin-sawa (大同心沢).
Head into the Daidoushin-sawa and continue up for about 30 minutes or so and you will come to a small frozen waterfall which can be easily soloed. A short way past this and around the corner you will find yourselves looking up at the 50m Ōtaki.
The first third is not too steep, but after that things steepen until the final 10m vertical pillar at the top. It can be climbed in a single pitch from the bottom, but it’s possible to belay on the left side near the start of the final pillar if you prefer. If you’re planning to top-rope the Ōtaki, make sure you’re climbing on double ropes.
At the top of the pillar the angle eases as you pass through a notch in the rock with an in-situ chain anchor running down the left wall. Beyond this you will emerge into the bowl-like upper sawa.
Many people just come for the Ōtaki itself, and after climbing it they will rappel off the chain anchor and hike back out the way they came in. If the snow conditions are safe and consolidated, however, you may wish to continue to the top of the Daidoushin-sawa. From the top of the sawa, you have two choices.
(i) You can climb the mixed gully behind the Daidoushin pinnacle to access the main summit ridge, from where you can either turn left and reach Iodake in about an hour, or turn right and hike over Yokodake to Akadake.
(ii) You can ascend the ramp leftwards under the south face of the Daidoushin pinnacle to access the top of the Daidoushin-ryo descent ridge, which can then be followed all the way down. You will emerge into the lower Daidoushin-sawa about 10 minutes above the hiking trail at its entrance, and then a left turn will lead you back to the Akadake-kōsen hut.
The Daidoushin-ryo descent ridge: