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Mt. Akagi Day Hike Guide | An Autumn Loop over Kurobiyama and Komagatake, from a Beginner's Point of View (Gunma)

2024.11.02

If you're looking for a mountain from Japan's 100 Famous Mountains list that you can climb in a day from Tokyo during autumn colour season, Mt. Akagi in Gunma Prefecture is the one I'd point you to. We walked the autumn loop that links its highest peak, Kurobiyama (1,828 m), with Komagatake along the ridge.

The short version: Akagi is a 100 Famous Mountain that gives beginners a real sense of achievement. About four hours of walking, a ridge path wrapped in autumn colour, views down over Lake Onuma, and Akagi Shrine on the lakeshore — a lot packed into one day. Below I'll go through the route, the difficulty, access, and what to wear for the big temperature swings of autumn, based on what I actually felt walking it.

For context, this was my first hike in three weeks, straight after getting over a cold. I was out of breath a lot. That does mean I can tell you honestly what the hard parts feel like for someone starting out.

Route overview (day hike, Kurobiyama–Komagatake loop)

• Area: Mt. Akagi, Gunma Prefecture / one of Japan's 100 Famous Mountains
• Highest peak: Kurobiyama (1,828 m)
• Our route: Kurobiyama trailhead → Nekoiwa (viewpoint) → Kurobiyama summit → Komagatake → descent → Akagi Shrine
• Walking time: About 4 hours
• Access: A day trip by car from Tokyo. You can start from one of the car parks around Lake Onuma
• Best season: For autumn colour, mid to late October. The altitude means autumn arrives here earlier than on the plains
• Difficulty: ★★☆☆☆ (beginner). No dangerous chain sections, but the stretch up to the summit is a steady steep climb over loose rock, so it asks for fitness and attention to your feet

What kind of mountain is Akagi? Faith, a lake, and a shrine

"Mt. Akagi" isn't actually a single peak. It's the collective name for a group of summits — Kurobiyama, Komagatake and others — arranged around Lake Onuma, a crater lake. The terrain is unusual: a caldera holding a lake and wetlands (Onuma and the Kakumanbuchi marsh), and it changes character completely with the seasons.

I chose Akagi for two reasons. First, it's reachable in a day from Tokyo and manageable for beginners. Second, Akagi Shrine stands on the lakeshore. This has been a mountain of worship for centuries, and the shrine is well known as a spiritual site. Getting the satisfaction of a climb plus a bit of history and culture in the same day is what drew me here.

Starting at the Kurobiyama trailhead — three weeks off, and autumn in the air

The first thing I noticed was how completely the season had turned. We left home at 4 a.m. and reached the trailhead around 6:30, with frost on the ground and real cold in the air — about 7°C as we set off. It had been three weeks since my last hike, with a cold in between, and I was breathing hard early on, telling my body to be patient with itself.

For warmth I wore a merino wool base layer, a thin long-sleeve over it, a fleece, and a rain shell on top. I'd also splashed out on new CW-X full-support tights (a Japanese support-wear brand) — the model that holds the knees and hips firmly. People I know rate them highly, so I made the investment. On a first hike back after time off, having my legs supported was genuinely reassuring. (More on clothing and gear further down.)

The trail climbs from the very start. Soft moss underfoot, trees just beginning to turn overhead. It was the kind of opening stretch where you want to stop at every single view.

The Nekoiwa viewpoint — Lake Onuma below, and you just stop walking

After a while you reach the first viewpoint, Nekoiwa ("cat rock"), an open spot that looks right down over Lake Onuma and makes an excellent rest stop. In front of us were hillsides turning red and gold, with the lake lying quietly in the middle of them. "Oh, that's beautiful" — it came out of me before I could think about it.

I'd seen photos online beforehand of the colour reflected in the water, and I'd been hoping for that. We didn't get the reflection that day, but the whole mountainside had turned, and by that point I already felt like I'd got what I came for. Autumn in the mountains is different every year and every day, depending on timing and weather. The view in front of me was good enough that saving the reflection for another visit felt fine.

The rocky climb — an hour of being fully in the present

Past Nekoiwa the route gets serious. From here it's about an hour of continuous climbing over rocks of every size, working out where to put each foot as you go.

Oddly, I found that hour of concentrating on my feet genuinely pleasant. Normally my head is full of what's coming or what's already happened, but climbing over rock, all my attention goes to this one step. Worry about the future and regret about the past both recede. I hadn't expected the kind of mindfulness that hiking creates to feel this good. I was out of breath, and yet I lost track of time.

For food that day I brought two onigiri (rice balls), and 1.5 litres of water to be safe. We took frequent breaks and kept a pace that didn't push too hard.

Kurobiyama summit (1,828 m) — frost columns and Mt. Fuji behind cloud

After the long climb we reached the summit of Kurobiyama (1,828 m), the highest point of Akagi. I did a little fist pump. The wind was cold at that height and the temperature was around 9°C. There's a spot just before the top where Mt. Fuji is visible, but cloud had spread across that direction and we didn't get to see it. The forecast had said clear. Mountains do this.

What stayed with me were the frost columns pushed up all over the ground, frozen in the morning cold and slowly melting as the sun climbed. It felt like watching the season change in real time. From a viewpoint a little past the summit, blue sky showed through gaps in the cloud in places. That mix of cloud and blue is very much a high mountain in autumn.

On to Komagatake and Akagi Shrine — closing out four hours

From the summit we picked up the ridge that connects Kurobiyama to Komagatake, walking a path surrounded by autumn colour and taking in Akagi from a new angle. After descending past Komagatake we finished at Akagi Shrine on the lakeshore, and it made a quiet ending to the day.

The satisfaction of a climb, autumn colour along a ridge, and history and a shrine at the end — having all of that inside roughly four hours is what makes this loop feel generous.

Clothing and gear (autumn, and the temperature swing)

The thing to plan for on Akagi in autumn is the temperature gap: morning versus midday, trailhead versus summit. On a day like ours — around 7°C at the trailhead, around 9°C at the top — you'll still sweat while climbing. Layering you can adjust piece by piece matters more than anything else.

• Base layer: A merino wool base that moves sweat away quickly. It keeps you from getting chilled by your own sweat
• Mid layer: A thin long-sleeve plus a fleece. Make sure you can take the fleece off while moving
• Outer: A rain shell (or wind shell) for wind and sudden rain. The ridge and summit wind drops the felt temperature sharply
• Tights / support wear: I used CW-X full-support tights. They take some of the load off the knees and hips on rocky ground, which helps if you've had time off or worry about descents
• Food and water: Snacks you can eat on the move plus something more substantial like onigiri. Around 1.5 litres of water is a good baseline in any season

Gloves and a thin beanie make a real difference too, both on a cold start and on a windy summit.

Final thoughts: a 100 Famous Mountain that suits an autumn debut

Having walked it, I think Akagi is genuinely well suited to a first autumn day hike. There are no dangerous chain sections, and yet the rocky climb gives you the feeling of having actually earned the summit. The view of Onuma from Nekoiwa, autumn colour along the ridge, the crisp air at the top, then the calm of Akagi Shrine — a varied day compressed into about four hours.

Even coming off a cold with three weeks away from the mountains, I got up it at my own pace with breaks. The two things that matter are layering you can adjust and a plan that isn't over-ambitious. Get those right and it should be a lovely day even if you're new to this.

If you can get a little way out of Tokyo this autumn, Akagi is a good place to climb your first 100 Famous Mountain of the season. I hope your walking days are full of coloured ridges and quiet lakes.

🛒 See the gear from the video as a list → A packing list for your first low-mountain hike

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