Mt. Sukai Hiking Guide (2026): The Long Ginzandaira Loop via Mt. Kōshin, Kōshin Sansō Hut, and the Closed Gunma Forest Road

Based on official information from Nikko City, Numata City, and Tochigi Prefecture, checked October 24, 2026.

Introduction

Mt. Sukai (2,144 m) is one of the 100 Famous Mountains of Japan, on the border of Nikko (Tochigi) and Numata (Gunma). It is known for having one of the longest approaches of any Hyakumeizan in Kanto. Nikko City's tourism site describes it as the main peak of the Ashio range.

In Short: Start at Ginzandaira; the Gunma Road Is Closed

• Gunma side (Sukai Bridge): Numata City reports that the Sukai Line (Neri–Kurihara forest road) is closed for the time being because of rockfall (page updated September 1, 2026). The shortest drive to the Sukai Bridge trailhead cannot be used.
• Tochigi side (Ginzandaira): Nikko City's tourism site gives 7.5 hours from the Ginzandaira parking lot to the summit, 12.5 hours round trip.

The Gunma side used to be the standard day hike. Numata City gives no date for reopening, so check its traffic page before you go.

Key Facts

Difficulty: Tochigi Mountain Grading

The Tochigi Prefecture Mountain Accident Prevention Council's mountain grading (revised September 2022; snow-free, good weather) rates the routes as follows.

At 14.1 hours and 26.5 km, the Sukai loop is one of the longest routes in Tochigi's table. The table notes that although there is a hut on the route, the distance from it is long. A day hike means a very early (pre-dawn) start, and a one-night plan using Kōshin Sansō is a realistic option.

The Route via Mt. Kōshin

Nikko City's "Ashio hiking information" describes the Mt. Kōshin course like this:

1. From Ginzandaira, follow the forest road along the Kōshin gorge to the first torii gate
2. After the Kōshin Seven Falls, climb the trail along the Minomozawa stream, once the approach to Sarutahiko Shrine
3. Pass Kagami-iwa rock, the Meoto-gaeru stones, and the Niō gate, then climb stone steps to the site of Sarutahiko Shrine
4. Soon you reach Kōshin Sansō. From the hut, continue past Urami Falls, Ichi-no-mon, and Ōtainai to the top of Mt. Kōshin
5. The summit of Mt. Kōshin has no view, but about 5 minutes farther is a viewpoint toward Mt. Sukai

From Mt. Kōshin the loop in Tochigi's grading goes over Mt. Nokogiri to Mt. Sukai, then returns to Ginzandaira via Rokurinpan Pass.

Closed sections

Nikko City reports that part of the trail on the "Kōshin path where the Yashio azaleas bloom" (Ginzandaira – first torii – Kōshin Sansō – Tenka-no-miharashi) was damaged and some sections cannot be used. From the Sarutahiko Shrine site, head toward Kōshin Sansō to go to Mt. Kōshin. No reopening date has been set. See the map on Nikko City's page, or ask the Tochigi Prefecture Kensei Environment and Forest Office (0288-21-1180).

Using Kōshin Sansō (Nikko City)

According to Nikko City, the hut reopened as an emergency hut on April 16, 2026.

• Free; no reservation needed; open all year
• About 10 sets of bedding, but bring your own sleeping bag
• Stream water is piped in from mid-April to early December; it is not sterilized, so boil it
• No warden, no meals, no electricity
• The area is a special zone of Nikko National Park, so tents are prohibited
• The toilet reopened on June 30, 2026 after breaking down from heavier use than expected. Nikko City asks hikers to bring a portable toilet if they can, and has set up a portable-toilet booth under the hut's west veranda. If overuse happens again, the toilet may be closed again.

Always submit a climbing plan (hiker card) when you set out.

Access

Ginzandaira is in Ashio, Nikko City. We could not confirm details of buses, taxis, or other public transport on official sites.

Gear

The trail is a regular hiking trail, but it is long and includes rocky sections.

• Hiking boots, rain gear, and warm layers
• A headlamp (essential for long days)
• Plenty of water (boil any water from the hut) and extra food
• A sleeping bag if staying at Kōshin Sansō, and a portable toilet
• An offline map app and a power bank

Season

Tochigi's grading assumes snow-free conditions and good weather; snow or bad weather changes the difficulty. Officially, the hut is open all year and the stream water runs mid-April to early December. From autumn, short days make timing on a day hike even tighter. See also bear safety in Japan.

Not Confirmed

• When the Gunma-side forest road will reopen (Numata City says only "for the time being")
• Up-to-date public transport and parking at Ginzandaira
• Current trail conditions near the summit (collapses, closures)
• When snow arrives (varies by year)

Summary

• Official guide time: 12.5 hours round trip from Ginzandaira (Nikko City)
• Tochigi grading for the loop: fitness 7, difficulty D, 14.1 hours, 26.5 km
• The Gunma-side Neri–Kurihara forest road is closed for the time being after rockfall
• Kōshin Sansō is a free emergency hut (bring a sleeping bag and a portable toilet; no tents)
• Don't insist on a day hike; consider a night at Kōshin Sansō

See also: Hyakumeizan day trips from Tokyo

References

• Nikko City — Ashio hiking information, including Kōshin Sansō (Japanese)
• Nikko City tourism — Mt. Sukai (Japanese)
• Numata City — Sukai Line (Neri–Kurihara forest road) closure (Japanese)
• Tochigi Prefecture — Mountain grading (Japanese) (2022 brochure, PDF)