How Do You Stay Safe from Bears and Mount Asama in Karuizawa?

Published 2026-10-04 · Sources checked 2026-10-04 · Treasure Hunting Co., Ltd.

This guide is for visitors and second-home owners who walk in Karuizawa's woods or look up at Mount Asama. It covers Asama's current volcanic alert level, where you may and may not climb, what to do if the volcano erupts, and how to avoid trouble with Asiatic black bears.

All of it comes from official pages: the Japan Meteorological Agency (JMA), Karuizawa Town and Nagano Prefecture. We read them on 4 October 2026. Alert levels and bear notices can change, so check the latest JMA and town notices before each outing.

Mount Asama's alert level today

JMA lists Mount Asama as a volcano under constant watch. Its summit stands at 2,568 metres. JMA uses five volcanic alert levels, from Level 1 to Level 5.

• At 11:00 on 22 May 2026, JMA lowered Asama from Level 2 (near-crater restrictions) to Level 1. The keyword for Level 1 is "be aware that this is an active volcano".
• JMA's list of warnings and forecasts for Asama showed no later change when we read it.
• JMA's bulletin still warned of a possible very small eruption affecting up to 500 metres from the summit crater. It asked people to follow local instructions and stay out of dangerous areas.
• The same bulletin asked people to watch for sudden ash emissions and volcanic gas.
• JMA's Asama alert level sheet says the area within 500 metres of the crater is off-limits even at Level 1.

JMA's English page explains when warnings start. Near-crater warnings are issued at Level 2 and Level 3. Warnings for residential areas are issued at Level 4 and Level 5.

You cannot climb Asama from the Karuizawa side

The town explains that even at Level 1, a 4-kilometre radius from the crater is a restricted zone on the Karuizawa side. It is closed under Article 63, Paragraph 1 of the Disaster Countermeasures Basic Act.

Only the trails up Ko-Asama and Mount Sekison are allowed. Everything else in the zone is closed. The town states plainly that you cannot climb Mount Asama from the Karuizawa side.

The town asks everyone to keep watching JMA's information. It links to JMA pages, including monitoring camera images and monthly activity reports.

If Asama erupts

The town's page on preparing for an eruption says Asama has been relatively quiet compared with the period from about 1900 to the 1970s. It also says no one knows when a damaging eruption may come. Its advice includes:

• Get into the habit of looking at Asama's plume. Notice any smell of sulphur, a change in colour or a larger volume.
• Carry a helmet against small volcanic rocks, and a mask and goggles for ash.
• In an eruption, listen to TV, radio, the town's public address vehicles and its disaster radio.
• Keep windows closed against ash. Avoid unnecessary travel, and if you are outside, shelter in a building or a car.
• When going out, wear a helmet, mask and goggles.
• To evacuate, move away from Asama, and avoid the downwind side where you can.

The town also warns about snowmelt lahars. If a mid-sized eruption happens while snow lies near the summit, a pyroclastic flow can melt it into a fast flow of mud and rock. Evacuate early from valley floors and low ground. Move away from valleys to higher ground.

If the mudflow has already reached you or is very close, do not go outside. Move to the second floor or higher of a strong building.

The town gives the JMA Asama Volcano Disaster Prevention Liaison Office, 0267-45-2167, as the number to call if you notice anything unusual on Asama.

Bears in Karuizawa this autumn

When Nagano Prefecture updated its bear page on 2 October 2026, no area of the prefecture was under a bear warning or advisory. The same page lists a bear injury in Karuizawa on 6 September 2026. A man was hurt in a forest while picking mushrooms.

The town reports the same incident at about 9:00 that day, in the national forest at Mitsuishi. It says bears at this time of year roam widely for food, which raises the risk of a run-in.

The town's bear programme page gives more background:

• There has been no bear injury in areas zoned for human activity since September 2010.
• The town had two injuries in fiscal 2025. Both happened in national forest.
• Sightings in fiscal 2025 reached 208, the highest on record. The town notes that some reports were serows or wild boars mistaken for bears.

Nagano Prefecture adds that about 70 percent of bear injuries in the prefecture happen in forests. Mushroom and wild plant gatherers are the largest group, about 20 percent of the total.

How to avoid meeting a bear

The town's advice is to behave as if bears are in the hills:

• Carry a bear bell, a radio or a whistle, so bears know a person is there.
• Dawn and dusk are when bears are most active. Avoid thickets with poor visibility, and avoid going into the hills at those times.
• Avoid going alone. Move in a group.
• If you find bear tracks or droppings, go no further and turn back.
• Do not enter forests that are closed to entry.
• Keep dogs on the lead. A barking dog can excite a bear and draw it closer.
• Never go near a cub. Its mother will be close by.

If you meet a bear

The town says to stay calm. Back away slowly and quietly, without provoking the bear. Do not run, because bears tend to chase things that run.

If you meet a bear at close range, protect your head with your hands and lie face down.

Food, rubbish, wild mushrooms and alerts

• Food and rubbish: food, pet food and kitchen waste left outside can teach bears to hang around buildings. Store them indoors or somewhere locked. Put rubbish out on the morning of collection day.
• Feeding: the town asks people never to feed wild animals. Feeding can also draw bears. If it causes harm to neighbours, it may be punishable under the animal welfare law.
• Wild plants and mushrooms: the town asks people not to pick, eat or sell certain wild plants or any wild mushrooms. For these plants, the prefecture has asked this since 2013, after radioactive caesium above food standards was found. Picking wild plants in national forest is banned.
• Alerts: the town sends free monkey and bear alerts through its official LINE account or by email. Sign-up details are on its page.
• Zoning map: the town's bear zoning map leaflet is handed out at the tourist information centres in Karuizawa and Naka-karuizawa stations, among other places.

What we could not verify, and therefore left out

• The town's live bear and monkey sighting map. It is run on an outside site, which we did not check.
• Whether the alert emails come in English. The sample messages on the town page are in Japanese.
• Details inside the town's PDF leaflets, the Asama hazard map and the restriction map. We did not check them line by line.
• Trail conditions and opening periods for Ko-Asama and Mount Sekison.
• Emergency phone advice for visitors. None of the pages we read for this guide covered calling 110 or 119.

Related guides

• How do you get to Karuizawa from Tokyo?
• What is Kyu-Karuizawa, and how did Karuizawa become a summer resort?

Sources

All URLs retrieved 2026-10-04.

1. 浅間山 (Japan Meteorological Agency) — (volcano under constant watch; 2,568 m)
2. 噴火予報：警報解除（浅間山）令和8年5月22日 (Japan Meteorological Agency) — (Level 2 to Level 1 at 11:00 on 22 May 2026; 500 m; follow local instructions; ash and gas)
3. 火山に関する情報の発表状況 浅間山 (Japan Meteorological Agency) — (no later warning or forecast listed)
4. 浅間山の噴火警戒レベル (Japan Meteorological Agency) — (five levels and keywords; 500 m closed even at Level 1)
5. Volcanic Warnings and Volcanic Alert Levels (Japan Meteorological Agency) — (when near-crater and residential warnings are issued)
6. 浅間山の噴火警戒レベルが引き下げ（レベル2→1）になりました (Karuizawa Town) — (4 km restricted zone, legal basis, Ko-Asama and Sekison trails, no climbing from the Karuizawa side, check JMA)
7. 浅間山の噴火に備える (Karuizawa Town) — (quiet since the 1970s; plume watching; helmet, mask, goggles; actions in an eruption; evacuation direction; snowmelt lahars; liaison office number)
8. 気象庁が発表する浅間山に関する各種情報 (Karuizawa Town) — (JMA information to check regularly)
9. ツキノワグマについて知っていただきたいこと (Nagano Prefecture) — (no warning or advisory as of 2 October 2026; 6 September Karuizawa injury; 70 and 20 percent)
10. クマ人身事故情報 (Karuizawa Town) — (6 September injury at Mitsuishi national forest; bears roaming for food)
11. 軽井沢町のツキノワグマ対策事業 (Karuizawa Town) — (no injury in human activity areas since 2010; fiscal 2025 injuries and 208 sightings; mistaken reports)
12. クマに注意をしましょう (Karuizawa Town) — (bells, dawn and dusk, groups, tracks, closed forests, dogs, cubs, encounters, food storage, rubbish)
13. 野生動物にエサを与えないでください (Karuizawa Town) — (no feeding; draws bears; possible penalty under the animal welfare law)
14. 山菜・野生きのこ採取の自粛について (Karuizawa Town) — (do not pick, eat or sell; caesium; since 2013; national forest ban)
15. さる・クマメールについて (Karuizawa Town) — (free alerts by LINE or email; sample messages in Japanese)
16. かるいざわツキノワグマゾーニングマップ (Karuizawa Town) — (zoning map leaflet and where it is handed out)