Let’s be honest up front, because most English-language pages about this mountain are not: as of early 2026, Kusatsu-Shirane is not a mountain you hike. It is a mountain you visit — by scenic drive, from designated viewpoints — and the distinction matters, because this is an active volcano under an elevated alert level.
Japan’s Meteorological Agency raised the volcanic alert for Kusatsu-Shirane to Level 2 on August 4, 2025, and volcanic unrest continued into January 2026. The close-up walk to the Yugama crater is currently suspended, with a roughly 1-kilometer no-entry zone around the crater. That situation can change — in either direction — so the single most important sentence in this guide is this one: check the current JMA alert level and the Kusatsu town notices before you visit, and plan around them.
What remains is still very much worth the trip: one of the most acidic crater lakes on Earth, glowing emerald green in a volcanic amphitheater; one of Japan’s great mountain drives; and below it all, Kusatsu Onsen — one of the country’s most famous hot-spring towns. This guide tells you how to do the trip properly and safely, with current fares, road information, and the real story of the 2018 eruption that everyone gets wrong.
Table of Contents
Quick Facts
| Mountain | Kusatsu-Shirane, 2,160 m, Gunma Prefecture |
| Main sight | Yugama crater lake — ~300 m wide, pH ~1.0–1.2, emerald green |
| Current status | JMA alert Level 2 (raised Aug 4, 2025); Yugama close-up walk suspended, ~1 km no-entry zone — CHECK CURRENT STATUS BEFORE VISITING |
| Experience type | Scenic drive + viewpoints + onsen town (not a summit hike at present) |
| Key road | Route 292 (Shiga–Kusatsu Kogen Route) — closed in winter, roughly mid-November to mid/late April |
| Access | Ltd. Express Kusatsu from Ueno ~2.5h (~¥5,130), or local trains via Takasaki ~3–3.5h (~¥2,940); bus Naganohara-Kusatsuguchi to Kusatsu Onsen ~30 min (~¥670) |
| Base | Kusatsu Onsen town |
The Volcano, Honestly: Alert Levels and the 2018 Eruption
Kusatsu-Shirane is a restless volcano, and understanding its current mood is part of visiting responsibly.
What Level 2 means
Japan’s volcanic alert scale runs from 1 (normal) to 5 (evacuate). Level 2 means “do not approach the crater” — exactly what the current ~1 km no-entry zone around Yugama enforces. The JMA raised Kusatsu-Shirane to Level 2 on August 4, 2025 after detecting increased volcanic activity, and unrest was still being reported into January 2026.
Alert levels move. Before you book anything, check the JMA’s volcanic information pages and the Kusatsu town official notices for the latest status. If the level has dropped, more of the mountain may be accessible; if it has risen, adjust or postpone. This is not bureaucratic box-ticking — it is how you stay safe on an active volcano.
The 2018 eruption everyone misattributes
Here is the correction that belongs in every guide to this mountain: the eruption of January 23, 2018 did not happen at Yugama. It happened at neighboring Mount Motoshirane, roughly 2 kilometers away. The 2018 event — which caught skiers at a nearby resort and made international headlines — belongs to Motoshirane’s story, not Yugama’s.
Why does this matter for your visit? Because confusing the two leads to exactly the wrong conclusion: that Yugama itself erupted in 2018 and is therefore “done.” Volcanoes do not work that way. Yugama’s current Level 2 status stands on its own recent unrest, regardless of what Motoshirane did eight years ago. Keep the two craters straight and you will read every official notice correctly.
Yugama: The Emerald Crater Lake
Yugama is the reason the drive up the mountain exists. The crater lake is about 300 meters across and famous for two things: its striking emerald-green color, which shifts with the light and the season, and its chemistry — with a pH around 1.0 to 1.2, it ranks among the most acidic lakes in the world. That acidity is why the water looks the way it does, and why you will be admiring it from a distance rather than dipping a toe in.
Under normal alert conditions, visitors view Yugama from the roadside viewpoint and parking area along Route 292, with a short walk to the crater rim. With the current Level 2 restrictions, the close-up walk is suspended and the crater is viewed from outside the no-entry zone. Check locally for exactly which viewpoints are open on the day of your visit — rangers and town notices will have the current map.
Even at a distance, Yugama is a genuinely strange and beautiful sight: a jewel-green lake steaming faintly in a bleached volcanic basin, with the ridgelines of the Shirane massif behind it. Bring a camera and a windproof layer — the viewpoint sits at altitude and the wind has opinions.
Getting There from Tokyo
Train to Naganohara-Kusatsuguchi
The gateway station is Naganohara-Kusatsuguchi on the JR Agatsuma Line. Two main options from Tokyo:
- Limited Express Kusatsu from Ueno: about 2.5 hours, roughly ¥5,130. The fastest and simplest choice — one seat most of the way.
- Local trains via Takasaki: about 3 to 3.5 hours, roughly ¥2,940. Slower and requires transfers, but significantly cheaper. A reasonable trade if you are not in a hurry.
Bus to Kusatsu Onsen
From Naganohara-Kusatsuguchi, the bus to Kusatsu Onsen town takes about 30 minutes and costs around ¥670. The bus drops you in the center of one of Japan’s great onsen towns — which is your base for everything that follows.
The mountain road: Route 292
From Kusatsu Onsen town, Route 292 — the Shiga–Kusatsu Kogen Route — climbs past Yugama and over the mountains toward Shiga Kogen. It is one of Japan’s celebrated highland drives, and the Yugama viewpoint sits along it.
The critical planning fact: this road closes for winter, roughly from mid-November to mid or late April depending on snowfall. Outside those months it is normally open — but volcanic restrictions can close sections independently of the season, so confirm the current open/closed status with Kusatsu town before driving up. If you are visiting in winter, plan the trip as an onsen-town stay and enjoy Yugama another season.
When to Go
The mountain is accessible roughly from late April to mid-November, bracketed by the Route 292 winter closure. June brings fresh green, summer offers the most reliable weather, and autumn colors arrive early at this altitude — typically October — painting the highlands around the steaming crater.
Winter, from mid-November, belongs to Kusatsu Onsen town itself: deep snow, steaming streets, and some of the best outdoor bathing in Japan. Many travelers deliberately choose winter for the onsen experience alone, with the understanding that the crater road is closed.
One more seasonal note: because access depends on both the road and the volcanic alert level, “when to go” has two answers. Check both before you commit — the road calendar and the JMA notices.
What to Pack
This is a sightseeing trip, not a hike, so pack accordingly:
- Warm layers and a windproof shell: the Yugama viewpoint is at high altitude and exposed. Even in summer it can be cold and windy up there.
- Comfortable walking shoes: for the viewpoint paths and for strolling Kusatsu town — not mountaineering boots.
- Camera: the crater lake’s color is the souvenir. Morning light is usually kindest.
- Swimwear and a small towel: not for the crater (absolutely not — pH 1.0), but Kusatsu Onsen town has public baths and foot baths worth using.
- Cash: mountain-area buses, parking, and small shops may not take cards.
- A printed or saved copy of the day’s access info: which viewpoints are open, the road status, the alert level — screenshot it all before you lose signal on the mountain road.
Where to Stay
Stay in Kusatsu Onsen town — there is no reason to stay anywhere else. It is one of Japan’s most famous hot-spring resorts, built around the spectacular Yubatake (hot water field) in the town center, where steaming mineral water cascades through wooden channels. The town has options across budgets, from large resort hotels to small family-run inns, and nearly all of them pipe the town’s famously hot, acidic spring water into their baths.
After a day of thin mountain air and crater viewpoints, there is no better recovery than a long soak. Give the town at least one night — two if you want a slow morning at the Yubatake and an unhurried drive up Route 292.
Our Tips for the Trip
- Check the alert level twice: once when planning, once the morning you drive up. JMA notices and Kusatsu town updates are the authority — not travel blogs, not this guide, not social media posts from last season.
- Do not plan a summit hike right now. However fit you are, the current restrictions mean the mountain is a viewpoints-and-onsen trip. Planning a hike you cannot legally do is how trips get ruined. Enjoy what is open — it is plenty.
- Get the 2018 story right. When someone in your group says “didn’t this erupt in 2018?” — that was neighboring Mount Motoshirane, about 2 km away, not Yugama. You will sound impressively well-informed, and you will read the warning signs correctly.
- Drive Route 292 in the morning. The light on Yugama is best before midday, the wind is often calmer early, and you avoid the afternoon tour-bus wave in peak season.
- Respect every rope and sign. Volcanic gas is odorless in some forms and the restricted zones exist for measured reasons, not caution theater. The viewpoint views are excellent — there is no need to go further.
- Winter visitors: embrace the onsen. The crater road is closed roughly mid-November to mid/late April. Come for the snow, the Yubatake lit up at night, and the baths — and put Yugama on the list for next summer.
Our honest summary: Kusatsu-Shirane right now is a spectacular half-day of crater viewpoints and mountain road plus one of Japan’s great onsen towns — not a hike. Done that way, with the alert level checked and expectations set, it is an excellent trip.
Frequently Asked Questions
Can you hike Kusatsu-Shirane at the moment?
Not currently in the normal sense. With the JMA alert at Level 2 (raised August 4, 2025), the Yugama close-up walk is suspended and a roughly 1 km no-entry zone surrounds the crater. Treat the mountain as a scenic-drive-and-viewpoint destination for now, and check the current JMA level and Kusatsu town notices before visiting — the situation can change.
What does volcanic alert Level 2 mean?
On Japan’s 5-level scale, Level 2 means “do not approach the crater.” It is a restriction on the crater area, not an evacuation — the onsen town and surrounding areas operate normally, with the exclusion zone enforced around Yugama itself.
Did Yugama erupt in 2018?
No — this is the most common error about this mountain. The January 23, 2018 eruption occurred at neighboring Mount Motoshirane, about 2 kilometers from Yugama. Yugama’s current alert status reflects its own volcanic unrest, separate from the 2018 event.
When is the Shiga–Kusatsu road open?
Route 292 (the Shiga–Kusatsu Kogen Route) is normally open from around late April to mid-November and closed through winter, roughly mid-November to mid or late April depending on snow. Volcanic restrictions can close sections independently of the season, so confirm the current status with Kusatsu town before driving.
Can you swim in Yugama?
Absolutely not. With a pH around 1.0–1.2, Yugama is one of the most acidic lakes in the world — the water would severely burn skin. It is also inside the current restricted zone. Admire the emerald color from the viewpoints; save the swimming for Kusatsu Onsen’s baths in town.
How do I check the current volcanic status before visiting?
Check the Japan Meteorological Agency’s volcanic information for Kusatsu-Shirane and the official notices from Kusatsu town. Do this when planning your trip and again on the morning of your drive — alert levels and restricted areas can change with little notice.
A Volcano to Respect, a Town to Love
Kusatsu-Shirane rewards the traveler who meets it on its own terms: check the alert level, drive the highland road, stand at the viewpoint and take in that impossible emerald lake, then descend to one of Japan’s great onsen towns for the evening. It is not a summit to bag right now — it is something better, a living volcano experienced properly, with respect. And when the alert level eventually eases, you will already know exactly where to go.
How We Would Plan the Trip and Its Cost
| Option | Time and fare in this guide | Added bus to Kusatsu Onsen | Rough one-way total |
|---|---|---|---|
| Limited Express Kusatsu from Ueno | About 2.5 hours, about ¥5,130 | About 30 minutes, about ¥670 | About ¥5,800 |
| Local trains via Takasaki | About 3 to 3.5 hours, about ¥2,940 | About 30 minutes, about ¥670 | About ¥3,610 |
The express costs about ¥2,190 more each way and saves roughly half an hour to an hour, so we would take it for a one-night trip and the local trains for a longer, slower stay. Our plan would be to arrive in time for the Yubatake and a bath on day one, then drive or bus up Route 292 on day two while the morning light is best, only if the road and viewpoints are open.
One caution: the alert-level details in this guide date from early 2026, so we would check the Japan Meteorological Agency and Kusatsu town notices again before booking anything. If the crater viewpoints are closed, the onsen town still makes a good trip on its own. For other volcanic days nearby, see our Mount Asama guide and Mount Nasu guide.
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