Kusatsu-Shirane-san (草津白根山, 2,160 m) is one of Japan's most active and closely monitored volcanoes, rising above the famous hot-spring town of Kusatsu Onsen in Gunma Prefecture. Its centrepiece is the Yugama (湯釜) crater lake, with a pH around 1.0 — among the most acidic bodies of water in the world. Unlike most Hyakumeizan peaks, there is currently no sanctioned hiking route to the summit crater: access is governed by volcanic alert levels, a standing precautionary exclusion zone, and persistent volcanic gas. This guide explains the access reality and how to plan a responsible visit.
Why Fukada Chose Kusatsu-Shirane-san
Kusatsu-Shirane-san is one of the hundred peaks in Kyuya Fukada's Nihon Hyakumeizan. The book's order runs roughly north to south and is not a ranking — Fukada did not number or rank the mountains. The draw is the Yugama crater lake, whose extraordinary acid colour and the sulphur that pervades the volcanic zone set this peak apart, together with the cultural weight it gains from neighbouring Kusatsu Onsen, one of Japan's most famous hot springs.
The Mountain
| Attribute | Detail |
|---|---|
| Shirane (Yugama-side) peak | 2,160 m (7,087 ft) |
| Massif high point | Motoshirane (本白根山), 2,171 m |
| Prefecture | Gunma |
| Volcano status | Active; JMA monitored; precautionary exclusion zone in force |
| Crater lakes | Yugama (湯釜), Mizugama (水釜), Karegama (涸釜) |
| Yugama acidity | pH ~1.0, one of the world's most acidic lakes |
| Book order | Roughly north-to-south, not a ranking |
| Access | No open route to the crater; check JMA alert level and road status |
The Shirane (Yugama-side) tourist peak stands at 2,160 m, but the overall highest point of the massif is Motoshirane at 2,171 m. The white, rocky barren look of the summit area dates from the 1882 eruption; before that the summit was vegetated. Three crater lakes sit on the mountain — Yugama, Mizugama and Karegama — of which the Yugama is the famous acid lake, with a pH around 1.0.
The Routes
There is currently no sanctioned hiking route to the Yugama crater rim. The crater sits inside a long-standing precautionary exclusion zone, and the visitor experience is road-based viewing rather than a summit climb.
Yugama viewing from the Route 292 area
Grade: Sightseeing (no climb to the crater)
When the National Route 292 (Shiga-Kusatsu Kogen Route / 志賀草津高原ルート) is open and the alert level permits, visitors can view the volcanic landscape from the road area. The road has a night closure and a no-stopping volcanic-gas zone. The precautionary no-entry zone of roughly 500 m (up to 1 km) around the Yugama crater applies even under the lowest alert level, so do not attempt to approach the crater rim.
The historic visitor access was the Shirane Volcano Ropeway (白根火山ロープウェイ), which closed after the January 2018 eruption and was permanently abolished (discontinuation announced 9 February 2018). It no longer operates, and there is no replacement lift or trail to the crater.
Getting There
Kusatsu Onsen is the natural base. From Tokyo, take the JR Shinkansen to Takasaki, then a bus to Kusatsu Onsen; direct express buses from Tokyo to Kusatsu Onsen also run.
From Kusatsu Onsen, road access to the volcanic area is via the National Route 292 / Shiga-Kusatsu Kogen Route. The road status is the key planning fact: the section between the Sessho gate (殺生ゲート) and the Manza junction gate (万座三叉路ゲート) is closed whenever the Yugama alert is at Level 2, and the route also has a night closure and a no-stopping volcanic-gas zone. Confirm the road is open and check the alert level before setting out.
Flora and Wildlife
In the active volcanic zone, the extreme acidity and sulphur gases limit vegetation, and there is no significant wildlife at the crater itself. The forested approaches below the volcanic zone support Asiatic black bears (ツキノワグマ) — the bear species found across Honshu — and typical Gunma mountain wildlife. Carry a bear bell on forested trails.
Seasonal Guide
The volcanic area is accessible mainly when the National Route 292 is open and the alert level permits; the road is subject to seasonal and night closures. In winter, a ski resort operates on the mountain, but access and conditions depend entirely on volcanic activity.
For context when setting expectations: the Yugama side was raised to alert Level 2 (crater-area restriction) on 4 August 2025 after a swarm of volcanic earthquakes and ground inflation, then lowered back to Level 1 around mid-May 2026. Even at Level 1 the precautionary exclusion zone and gas hazard remain. Always verify current conditions before travelling.
Practical Tips for Foreign Visitors
Volcanic alert system. Japan's JMA rates volcanoes on a 1–5 scale. At Level 1 a precautionary no-entry zone around the Yugama crater still applies; Level 2 adds a crater-area restriction and the Route 292 gate closure; higher levels restrict access further. Check the alert level before every visit.
The 2018 eruption. The January 2018 phreatic eruption occurred at Motoshirane, a separate vent. A single fatality — a Self-Defense Force member on ski training — was caused by ballistic volcanic blocks, not an avalanche; an avalanche account was given initially by defense officials and later formally retracted. Around eleven people were injured by volcanic blocks and broken glass, and ballistics shattered the windows of the ropeway gondola. The event is a reminder that phreatic eruptions can strike without precursor warning.
Kusatsu Onsen. The town below is one of Japan's most famous onsen resorts, centred on the open-air Yubatake (湯畑) hot-spring field. The yumomi paddle-stirring and dance show is staged inside the Netsunoyu (熱乃湯) hall beside the Yubatake — not at the Yubatake itself — at fixed daily show times (mornings around 9:30/10:00/10:30 and afternoons around 15:30/16:00/16:30), with an admission fee. Allow time for the onsen experience before or after visiting the volcanic area.
Frequently Asked Questions
Can you hike to the Yugama crater of Kusatsu-Shirane-san?
No. There is currently no sanctioned hiking route to the Yugama crater rim. A precautionary no-entry zone of roughly 500 m (up to 1 km) around the crater applies even at the lowest alert level, so the visitor experience is road-based viewing rather than a summit climb.
How do you get to Kusatsu-Shirane-san without a car?
Use Kusatsu Onsen as your base. From Tokyo, take the JR Shinkansen to Takasaki and then a bus to Kusatsu Onsen; direct express buses from Tokyo to Kusatsu Onsen also run. From Kusatsu Onsen, the volcanic area is reached via the National Route 292 / Shiga-Kusatsu Kogen Route.
Is the Yugama ropeway still running?
No. The Shirane Volcano Ropeway, the historic visitor access, closed after the January 2018 eruption and was permanently abolished (discontinuation announced 9 February 2018). There is no replacement lift or trail to the crater.
Do I need to check the volcanic alert level before visiting?
Yes. Japan's JMA rates volcanoes on a 1–5 scale, and access depends on it. At Level 1 a precautionary no-entry zone around the Yugama crater still applies; Level 2 adds a crater-area restriction and closes the Route 292 gate between the Sessho gate and the Manza junction gate. Check the alert level and confirm the road is open before every visit.
Are there bears around Kusatsu-Shirane-san?
The forested approaches below the volcanic zone support Asiatic black bears (ツキノワグマ), the bear species found across Honshu. There is no significant wildlife at the crater itself due to the extreme acidity and sulphur gases. Carry a bear bell on forested trails.
This guide is part of the Japan's 100 Famous Mountains: Complete Hyakumeizan Guide series.
