[Aichi/Tahara Alps] Mt. Oyama & Nanatsu-yama 42km Loop | The Day I Stalled on a Winter Low-Mountain Long Trail

The so-called "Tahara Alps" in Tahara City, Aichi Prefecture.
Although the elevation is not high, the mountain range on the peninsula, with its repeated ups and downs, is a tougher area than you might imagine.

On this day, the area was covered by a high-pressure system, and the forecast called for light winds.
The timing to finally walk the "around Tahara" route I had been eyeing for a long time had finally arrived.

In this article, I have summarized:

・The actual experience of the 42km loop including Mt. Oyama and Nanatsu-yama
・Confusing junctions and points of caution
・The reality of making refueling decisions on a long trail

I have compiled these points.

Hiking Overview

• Mountain Names: Mt. Oyama, Nanatsu-yama, etc. (Tahara Alps Loop)

• Region: Tahara City, Aichi Prefecture

• Date: February 14, 2026

• Weather: Sunny

• Course: Loop starting and ending at Gongen-no-mori Parking Lot

• Distance: 42.5km

• Cumulative Elevation Gain: 2,273m

• Activity Time: 9 hours 38 minutes (52 minutes of rest)

Looking only at the numbers, it is a low-mountain long trail, but
the actual experience is a "solid long traverse."

Overall Course Map

Walking by connecting the mountains of Tahara City, starting from Gongen-no-mori Parking Lot

Reasons for choosing this mountain

• High-pressure forecast with light winds

• Better viewing conditions than last time

• I want to check how the trail running pack feels

• A route around Tahara I've been eyeing for a long time

• The miso katsu after the finish is also a secret pleasure

It was a day when the weather and my goals aligned.

Course overview and impressions

▷ Trailhead to Mt. Fujio (before dawn)

Started at 5:00 AM.
I moved silently through the darkness.

The descent from Mt. Fujio is steep.
I would prefer to pass this slope after it gets light, but the days are still short in winter.

By the time I finished the descent, the sky finally began to color.
The time between the night view and the sunrise is a quiet reward for this course.

▷ Mt. Nishiyama to Mt. Oyama (the core of the first half)

Running on the road, I saw Mt. Nishiyama in the distance.
I realized the distance, thinking, 'I'm going all the way there?'

The view opens up from Hikari-iwa,
and when I wondered what the big mountain in the distance was, it turned out to be Mt. Oyama, where I was headed (lol).

Before Mt. Oyama is Oniotoshi.
The ups and downs unique to the peninsula continue.

When I arrived at Mt. Oyama,
it felt a bit strange to be standing on the mountain with the steel tower I had been looking at from afar.

▷ Mt. Oyama to Nanatsuyama (the wall of the second half)

Looking back, Mt. Oyama is already far away.
Having come this far, the scale of the Nanatsuyama mountain range is clearly visible.

And then, reality.
Nanatsuyama has seven peaks.

Once the climbing started, my pace gradually slowed down.
It felt like the 30km wall in a full marathon.

Crossing the four visible peaks one by one.
It's not flashy, but there's nothing to do but keep at it.

▷ Final stretch to descent

The final mountain massif where the steel towers of Mt. Choko-ji stand out.
By the time I reached this point, I felt a mix of relief.

On the way, the 1L of water I brought wasn't enough,
so I restocked at FamilyMart. Making realistic decisions is important on long runs.

I was genuinely happy when I arrived at the final peak, Mt. Kinugasa.

After walking along the road, I reached the goal.

And to wrap it up, miso katsu.
It soaked into my tired body.

Course Conditions & Precautions

■ Very many junctions

The Wanko route section is well-maintained, but there are many junctions, so checking signs is essential.

■ The descent from Mt. Fujio is steep

It is slippery during the leaf-fall season. Be careful when passing through in the dark.

■ Partially unclear after the Hikari-iwa trailhead

Checking your position on the map is recommended.

■ Nanatsu-yama is mentally draining

Continuous ups and downs. Take this on assuming you still have energy in your legs.

■ Resupply plan

Even in winter, 1L of water is not enough.
For 42km, it is safer to assume you will need to resupply along the way.

▷ Recommended for

• Those who want to test their endurance for long distances

• Those who enjoy low-mountain traverses

• Those who want to combine it with trail running practice

Looking back

It was a day that required more decision-making than the numbers suggest.

Deciding whether to pass before dawn.
Misjudging the amount of supplies.
Stalling at Nanatsu-yama.

Still, I managed to walk the whole way.

I mainly hike mountains in Shizuoka, but
when I hike long trails in low mountains of other prefectures like this, I get a clear sense of where I currently stand.

Next time, I will be a little stronger.

I continue to hike while valuing "conditions and judgment" in the same way.
I would be happy if you followed me.

Reference links

▶ Click here for this month's summary