Route Name: Onba-yama Nishi-runze (御場山 西ルンゼ) F1
Mountain: Mt Onba (1059m, 御場山)
Map sheet: 21 [Yama-to-kougen-chizu (山と高原地図) series]
Approach: 30 minutes
Grade: WI3 (good conditions) / WI4 (thin conditions)
If travelling by car from Tokyo (東京), take the Kan-etsu Expressway through Saitama, and then change onto the Joshin-etsu Expressway at the Fujioka junction (藤岡). Leave the Joshin-etsu at Shimonita Junction (下仁田) in Gunma prefecture, and make your way onto Route 254. Drive along the 254 with the river on your left until you come to a junction, and turn right onto Route 43. Continue up this road until you reach a small village.
Take a left and drive up a narrow road for a short way, and park at end of the road next to a house and some terraced fields. There is space for a couple of cars. From here you will continue on foot.
Walk about 50m down to the river, and cross to the other side.
Walk up the path between some old wooden buildings.
Continue along the trail on the right side of the sawa for about 10 minutes and you'll come to a fork in the sawa. Cross the sawa here and walk up the left fork.
The F1 icefall is about 100m up the left fork on the left side.
It is approximately 30m high, and should be around WI3 in fat conditions. In thinner conditions, as seen in these photos, it is about WI4. There are trees to anchor from at the top, and a top-tope can be set from there with a 60m rope.
There is more ice above F1, but not as big as this, and we didn’t go there. It could be worth checking out though.
Gearing up at the start:
Nice steady climbing most of the way, with a steeper section near the top. Make sure that you either have a 60m rope or two 50m ropes.