[Southern Alps Deep South] Kaze-irazu, Mt. Daimugen, and Mt. Asahi | A record of decision-making for a 2-day, 1-night core loop during the lingering snow season, featuring steep climbs and narrow ridges

Introduction

I completed a tent-stay loop in the Deep South of the Southern Alps, from Sumatakyo, Shizuoka, covering
Kaze-irazu to Mt. Daimugen to Mt. Asahi.

This is a route I have wanted to hike for a long time.
I have missed the chance several times and even had to turn back once due to forgotten gear.
But this time, the timing finally aligned.

In this article, I will summarize based on my actual experience:

・The state of the steep climbs and narrow ridges in the core section
・Route decision-making during the lingering snow season
・Points to note when hiking with tent-stay gear
・Countermeasures for a course with no water sources

I will summarize these based on my actual experience.

It was a two-day trip where I felt the silence and severity characteristic of the Deep South.
I hope this will be helpful for those who want to challenge the Deep South in the future.

Hiking Data

Mountain Name: Kaze-irazu, Mt. Daimugen, Mt. Asahi
Region: Southern Alps Deep South (Shizuoka Prefecture)
Date: April 26-27, 2025 (2 days, 1 night)
Weather: Day 1: Cloudy then sunny / Day 2: Sunny
Course: Sumatakyo -> Mt. Kurishiro -> Kaze-irazu -> Mt. Daimugen -> Sanporei (tent stay) -> Mt. Hinata -> Mt. Asahi -> Sumatakyo
Distance: 35.3km
Cumulative Elevation: +3733m
・Day 1: 20.9km / +2991m
・Day 2: 14.3km / -2337m
Activity Time: 20 hours 11 minutes

The course difficulty is "tough".
It was exactly as the numbers suggested.

Overall Course Map

A loop route connecting Sumatakyo to Kaze-irazu, Mt. Daimugen, and Mt. Asahi.
It is characterized by a long ridgeline and many ups and downs.

Reasons for choosing this mountain

・First tent stay of the season
・Akayashio (Rhododendron quinquefolium) season
・Wanting to connect the ridgelines of the Deep South

And above all, the feeling that "it's finally time to hike it."

I believe the Deep South is a region that tests not only physical strength but also
judgment and concentration.

Course conditions and impressions

■ Sumatakyo to Mt. Kurishiro

A steep climb from the beginning.
The direct ascent just below Mt. Kurishiro is quite steep and is not a warm-up.

There are "footpaths that make you want to descend" at forest road junctions and mountain passes, but it is important not to neglect route confirmation.

■ Kurishiro-yama to Kazeirazu (First half of the crux)

The atmosphere changes completely once you pass the Omori Station junction.

・Narrow ridges
・Steep climbs mixed with rock
・Choosing between direct ascents and bypass trails

There were also sections where I had to use all fours while carrying tent gear.

The section just before Kazeirazu (on the yellow tape side) is particularly steep.
The footing is unstable, and I felt it required even more caution on the descent.

However, looking back at the ridge I had walked.
The gentle colors of the Akayashio azaleas.
It is because of this scenery that I can keep moving forward.

■ Kazeirazu to Mt. Daimugen

I was genuinely happy when I stood on Kazeirazu.

The presence of Mt. Daimugen visible from there.
And the mountain ranges of the Deep South.

There is lingering snow just below Mt. Daimugen.
Furthermore, the ridge on the descent to the west is wide, and the trail is unclear.

Lingering snow × wide ridge = risk of losing direction

I checked the direction of travel frequently

■ Decision at Sanporei (Changing the tent site)

Originally, I planned to camp at the summit of Mt. Daimugen.

However,

・Presence of snow
・Strong winds
・Forecast for dropping temperatures

led me to decide to push on to Sanporei instead.

In the end, this decision was the right one.

Sanporei offers spectacular views, and I was able to enjoy the sunset and sunrise at a leisurely pace.

The time when the ridgeline of the Deep South is quietly bathed in color is truly exceptional.

■ Sanporei to Mt. Asahi (Second half of the core section)

The second day is mostly a descent.
However, it is not easy.

・The wide ridge around 1950m
・Navigating the double ridgeline
・The saddle around Koppazawa-no-kashira
・Confirming the descent point to the Senzu Dam

There are many points where the direction changes, so you must always be aware of your current location.

The area around the Gorinzawa entrance is a steep slope mixed with rocks.
Before Mt. Asahi, there is a narrow ridge with some brush.

You cannot let your guard down until the very end.

Course Conditions and Points of Caution

✔ The intense climb on the first day

The section from Mt. Kurishiro to Kaze-irazu is a series of steep climbs.
It is easy to lose your balance with camping gear.

✔ Before Kaze-irazu (yellow tape)

A steep climb that requires using all four limbs.
Proceed with caution even if it is dry.

✔ Lingering snow section on the west side of Mt. Daimugen

The trail is prone to disappearing.
There is a possibility of losing your way on the wide ridge.

✔ Ridge transition from Sanporei to Hinata-yama

The ridge is wide horizontally, making it easy to take the wrong direction.

✔ No water sources

There are no water sources on the route.

Brought this time:
・Water 4.3L
・Oral rehydration solution 0.5L
・Other beverages

As a result, I had about 1L left over.
Depending on the temperature, I felt that having a little extra was just right for this trip.

✔ Recommended for those who

・Are accustomed to long hours of activity
・Can perform route finding
・Have no resistance to steep climbs and narrow ridges

This is not for beginners.

Reflections

Kaze-irazu, a place I wanted to hike.
I finally stood there.

The presence of Mt. Daimugen.
The evening view from Sanporei.
The Deep South dyed in the morning sun.

It was a route that tested both my physical strength and judgment,
but that is exactly why it was such an intense two days.

Focusing on the mountains of Shizuoka,
I will continue to enjoy these "quiet traverses" in the future.

One more ridge in the Deep South has been connected.
Which ridge should I head to next?

Reference links

▶︎Click here for a 3-day, 2-night grand loop walking through the Deep South | Sumatakyo to Mt. Kuroboshi loop

In the Deep South, the character of the terrain changes completely with every ridge.
Details of when I climbed the Marubon-dake east ridge directly are summarized here.

▶︎ [Marubon-dake East Ridge | A record of the core route through dense brush and late-season snow (32km / ±3,437m)]