Mountain: Yokodake (横岳) on the Yatsugatake (八ヶ岳) massif
Map sheet: 32 [Yama-to-kougen-chizu (山と高原地図) series]
Time: 6 hours to summit ridge
Difficulty: WI5- / overall grade 3 winter alpine route
Take a Super Azusa express train from Shinjuku (新宿) to Chino (茅野 approx. 3 hours). Outside the JR station at Chino take a bus to Minotoguchi (美濃戸口 approx. 1 hour). This is the gateway to the Akadake-kōsen side of Yatsugatake. From the car park start hiking up the trail that is signposted to Akadake. The walk-in takes around 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 the Minoto-sansō (美濃戸山荘) hut that makes a good resting point for 5 minutes. The next hour follows the road until it finishes at a bridge across the sawa. From the other side the path narrows and meanders alongside the sawa (stream) for another hour or so until you reach the hut at Akadake-kōsen. This hut serves as basecamp for all the routes in the area.
On the approach:
The Akadake-kōsen hut:
I recommend scoping out the approach to the route in the light the day before, as it would be very easy to miss the turn off in the dark after an early start. Start by following the hiking trail in the direction of the pass at the start of the Nakayama ridge (中山尾根). After only about 15 minutes you need to peal off to the left and head up into the start of the Sansahou runze gully. You should have the Sekison (石尊尾根) ridge to your right once you get to the gully.
Looking back from the start of the climbing:
The first section of the route consists of about 5 frozen waterfalls of varying lengths up to 10m in height separated by stretches of step-kicking up steep snow inside the gully. Depending on conditions, the first waterfall could range from fairly fat and banked out at the bottom to extremely meagre. Protection throughout these first few hundred metres is ice screws in the waterfalls. 3-4 pitches should suffice to reach the end of this section.
The first ice pitch:
Inside the gully:
Eventually a large open ledge is reached, which marks the end of the narrowest section of the gully. This makes a good spot for a breather and a bite to eat. From here there are two possible directions, heading up a frozen waterfall left or right. The route takes the right fork. From here the angle eases off a little and the route continues up onto the upper face via more short ice sections interspersed amongst stretches of steep snow. The face opens up gradually, and the rock gendarmes of the Daidoushin (大同心) and kodoushin (小同心) can be seen off to the left.
First ice step after the ledge:
When you reach a headwall you need to move out right, up and around a corner to a peg belay on the upper section of the Sekison ridge. From here traverse a full ropelength along the underside of the headwall, with an in-situ peg and sling for protection halfway. Regroup at the end of this traverse, and then move up and right for another 80m to meet the hiking trail on the summit ridge.
On the traverse:
Once on the trail, head left up the ridge to the summit of Yokodake (横岳), or right towards Akadake (赤岳). After about an hour of moving along the ridgeline to the right it flattens out a little, eventually reaching a junction marked by a stone Buddhist statue of Jizo. The statue marks the entry point to the Jizo ridge on the right, and this is the quickest descent back to the Akadake-kōsen hut. This path is steep but straightforward. After about an hour of descent, and a 30 minute traverse over a low ridgeline you should arrive back at the hut you left that morning.
Summit of Akadake (赤岳):
Looking across to Amidadake (阿弥陀岳):
A superb gully route up the face to the left of Sekison Ridge, with a stunning and airy traverse to gain the summit ridge. One of the classic winter gully routes in the area, although ice conditions can be fickle some years. Take a rack of ice screws, and a selection of slings and quickdraws for protection.