Mount Akagi: Highland and Lakes Formed by a Volcano

Mt. Akagi is one of the "Jomo Three Mountains" alongside Mt. Haruna and Mt. Myogi, and a symbol of Gunma Prefecture. It is a majestic mountain of multiple peaks centered on its highest summit, Kurobi (1,828 meters), and its summit area holds the beautiful crater lakes Onuma and Konuma, born of volcanic activity. The highland plateau at the top is popular for outdoor recreation across the seasons, offering hiking, lake activities, and winter smelt fishing.

Highlights

The centerpiece of Mt. Akagi is Onuma, the crater lake that spreads across its summit. Sitting quietly at about 1,300 meters, Onuma is ringed by mountains, and along its shore stands Akagi Shrine, whose vermilion halls reflect beautifully on the water. Reached by crossing a bridge over the lake, the shrine is a popular photography spot for the mirror image of its halls on the surface. Summer brings boating, camping, and lakeside strolls in the refreshing highland air, while the other crater lake, Konuma, has a quieter character, with fine views from the promenade that circles it.

Enjoying the Seasons

Mt. Akagi is popular for hiking suited to everyone from beginners to seasoned climbers, with trails to the summit of Kurobi and lakeside promenades chosen to match one's fitness and level. In the bright green of early summer, colonies of azaleas bloom across the mountain, and it is especially known as a spot for renge-tsutsuji azaleas. Autumn brings brilliant foliage, with the colorful trees mirrored on the lake creating spectacular scenery. In winter Onuma freezes over and draws many anglers as a famous spot for ice fishing for smelt. Throughout the year, the mountain reveals a different charm each season.

Access & Basic Information

• Location: Akagisan, Fujimi-machi, Maebashi City, Gunma Prefecture, and surrounding areas
• By train: From Maebashi Station on the JR Ryomo Line, take a bus toward the summit (Onuma); the trip takes roughly a little over an hour each way
• By car: A convenient drive to the summit from the Akagi IC on the Kan-Etsu Expressway and other exits
• Elevation: Kurobi 1,828 meters; the Onuma lakeshore is about 1,300 meters
• Climate: High elevation keeps it cool even in summer, so bring a layer

Practical Travel Notes

The area around summit-level Onuma stays cool even at the height of summer, and mornings and evenings can be chilly, so an extra layer keeps you comfortable. In winter the roads freeze and gather snow, so winter tires or chains are essential if driving. Smelt fishing opens only after the ice has thickened sufficiently, so check the timing and whether stepping onto the ice is permitted in advance. The Kurobi trail includes rocky sections, so trekking shoes are advisable. Shops and eateries are scattered along the shore, but their operating seasons vary, so it is wise to confirm ahead.

A Word of Advice

The appeal of Mt. Akagi is the ease of driving all the way to the summit combined with the chance to enjoy both serious hiking and casual recreation. If time allows, enjoy a lakeside walk at Onuma and a visit to Akagi Shrine, then continue to Konuma to take in the quiet crater-lake scenery. With azaleas in early summer, foliage in autumn, and smelt fishing in winter, the tabitabi JAPAN editorial team hopes you will enjoy this symbol of Gunma throughout the year.

📚 Sources

The content here is organized from official tourism information on the Mt. Akagi area, Maebashi City guidance, public information on facilities around Lake Onuma, and on-site guidance. The business seasons of shops and eateries and the opening of pond-smelt fishing change by season. Roads freeze and see snow in winter. Because fees, hours, and access can change, please confirm with official sources before you set out.

Visitor Checklist

• Time needed: A half day for a stroll around Lake Onuma, or a full day including a climb such as Mt. Kurobi.
• What to bring: Around Lake Onuma near the summit the air is cool even in midsummer and it chills morning and evening, so bring an extra layer. The Mt. Kurobi trail has rocky sections, so trekking shoes are reassuring for climbing.
• Suggested route: Stroll the shore of Lake Onuma and, according to your fitness, enjoy a climb such as Mt. Kurobi or lakeside activities.
• Winter note: Roads freeze and see snow in winter, so winter tires or chains are essential if driving. Pond-smelt fishing opens only after the ice is thick enough, so confirm the timing and whether the ice can be entered in advance.
• Combining nearby: Shops and eateries dot the lakeside, but business seasons vary, so confirming in advance is reassuring.

Practical Information for Your Visit

• Data on Lake Onuma: A caldera lake at an altitude of 1,345 metres, with an area of 88 hectares and a maximum depth of 16.5 metres
• Main peak: Mount Kurobi (altitude 1,828 metres)
• Ice fishing for pond smelt (2026): The season opened at 7:00 on Thursday 15 January 2026, and access onto the ice was permitted from the same day. The 2026 season ended on Thursday 5 March. In a typical year, ice hole fishing runs from early January to the end of March, from 7:00 to 16:00.
• Notes on the ice: Access onto the ice is strictly limited to 7:00-16:00, including for those who are not fishing. Some areas are off limits because the ice is unstable, and the authorities urge visitors never to enter them.
• Fishing fees: One-day ticket 800 yen (free for junior high school students and younger), annual ticket 5,500 yen (valid from 1 September to 31 August the following year)
• Tents on the ice: Dome tents are prohibited; only snail-shaped tents may be used. If you use a heater inside a tent, adequate ventilation is essential.
• Enquiries about pond smelt fishing: Akagi Onuma Fisheries Cooperative (Aoki Ryokan) 027-287-8511
• Boats and canoes: Canoes and kayaks may be used from 1 June to 31 October. Rowing boats cost 600 to 800 yen for 30 minutes, and a motorboat trip around Lake Onuma costs 3,000 yen for 2 people. Bookings are in principle accepted online until 17:00 the day before. Rentals may be unavailable in rain or strong winds.
• Winter closure of prefectural roads (fiscal 2025): On Prefectural Route 16, the Ogo-Akagi Line, the 9.1 km section from Naegashima-machi, Maebashi City (the Akagi Onsen entrance) to Akagiyama, Fujimi-machi, Maebashi City (near Lake Konuma) is closed from 10:00 on 16 December 2025 to 10:00 on 6 April 2026. On Prefectural Route 251, the Numata-Akagi Line, the 11.1 km section from Sunagawa, Tone-machi, Numata City (the former toll road tollgate) to Fujimi-machi, Maebashi City (the junction with the Lake Onuma loop road) is closed from 14:00 on 5 January 2026 to 10:00 on 19 March 2026. The scheduled reopening dates and times may change depending on snow conditions.
• Route to the summit area during the winter closure: Gunma Prefecture advises using Prefectural Route 4 and fitting winter tyres. The start date of the fiscal 2026 (2026-27) closure had not been announced at the time of writing, so check the Gunma Prefecture road restriction information.
• Winter equipment: Studless winter tyres are required in winter. The temperature near the summit is 10 to 15 degrees lower than in the city below, so warm clothing is essential.
• Access (public transport): About 70 minutes by Kan-etsu Kotsu bus from stop 6 at the bus terminal outside the north exit of JR Maebashi Station. On weekdays you change at Fujimi Onsen; on Saturdays, Sundays and public holidays there is a direct Mount Akagi service. The current terminus is Akagi Hiroba-mae.
• Access (by car): About 40 minutes (roughly 25 km) from the Akagi IC interchange on the Kan-etsu Expressway to Lake Onuma in the summit area, about 60 minutes (roughly 31 km) from the Maebashi IC, and about 60 minutes (roughly 38 km) from the Isesaki IC on the Kita-Kanto Expressway
• Enquiries: Mount Akagi General Tourist Information Office 027-287-8061

Note: No official information has been published on the fees or capacity of the car parks around Lake Onuma. (Sources: Maebashi Tourism and Convention Association, Maebashi Marugoto Guide; Gunma Prefecture Road Management Division; official website of Maebashi City)