Mt. Iide (Iidesan) Hiking Guide (2026): Dainichisugi, Tengudaira (Daigura Ridge & Marumori Ridge), Unmanned Refuge Huts, and Trailhead Access

Straddling the borders of Yamagata, Fukushima, and Niigata prefectures inside Bandai-Asahi National Park, the Iide Mountain Range (飯豊連峰, Iide Renpo) is one of Japan's grandest and most rugged alpine massifs. Although its main peak, Mt. Iide / Iide Honzan (飯豊本山, 2,105 m), and the range's highest peak, Mt. Dainichi (大日岳, 2,128 m), sit just above 2,100 meters, winter winds off the Sea of Japan bury these ridges under some of the deepest snowpacks on Earth. As a result, expansive snowfields (万年雪), dwarf stone pine scrub, and alpine flora—including the endemic Iide-rinpu (イイデリンドウ)—thrive above a low tree line that feels every bit like a 3,000-meter range in the Japan Alps.

Wait times, long elevation gains (over 1,600 meters from the valley floor), and the fact that every hut on the upper ridge is an unmanned refuge hut (無人避難小屋) where you must carry your own sleeping bag, mat, stove, and food place Mt. Iide among the most physically demanding of the 100 Famous Japanese Mountains (Hyakumeizan).

Why Is Mt. Iide in Yamagata and Niigata if the Summit Shrine Strip Is Fukushima Prefecture?

One of the most famous geographical quirks of Mt. Iide is the "strip border" (盲腸県境) along the ridge from Mikunidake (三国岳) through Korenge (種蒔山) and Mt. Iide Honzan (飯豊本山) to Onishi-dake (御西岳):

Because Iideyama Shrine (飯豊山神社), worshipped since ancient times from the Aizu (Kitakata) side, owns the narrow worship trail (表参道) and the shrine precincts on the summit of Iide Honzan, a ribbon of land roughly 90 cm (3 shaku) wide along the trail and around the summit shrine belongs to Kitakata City, Fukushima Prefecture, cutting right between Iide Town (Yamagata) and Aga Town (Niigata)!

Official Route Grading & Comparison of the 3 Main Yamagata Routes

All grading figures below are taken directly from the Yamagata Mountain Information Portal — Mt. Iide (Hyakumeizan No. 085), the Yamagata Prefecture Mountain Grading List (PDF), and the 10-Prefecture Hyakumeizan Grading Route List (PDF):

Route	Trailhead	Physical Fitness Grade (1–10)	Technical Difficulty Grade (A–E)	Official Round-Trip Walking Time	Round-Trip Distance	Cumulative Ascent / Descent	Key Characteristics
1. Dainichisugi Course (`大日杉コース`)	Dainichisugi Goya (`大日杉小屋`) (Iide Town, ~605 m)	8 (1N2D–2N3D)	C	14h 20m	18.0 km	+2,150 m / -2,150 m	Shortest route to Iide Honzan; starts with the steep chain-equipped Zangezaka (`ざんげ坂`) climb to Jizodake, then climbs past Kiritachi Hut (`切合小屋`) and Kusariyama (`草履塚`).
2. Marumori Ridge Course (`丸森尾根コース`)	Tengudaira / Iide Sanso (`天狗平・飯豊山荘`) (Oguni Town, ~460 m)	9 (1N2D–2N3D)	C	16h 25m	23.0 km	+2,495 m / -2,495 m	Steep initial climb up Marumori Ridge to Mt. Kitamata (`北股岳`, 2,025 m) and Kairagi Hut (`梅花皮小屋`), then a grand ridge walk across Mt. Eboshi (`烏帽子岳`) and Onishi-dake (`御西岳`) to Iide Honzan.
3. Daigura Ridge Course (`ダイグラ尾根コース`)	Tengudaira / Iide Sanso (`天狗平・飯豊山荘`) (Oguni Town, ~460 m)	10 (2N3D)	D	18h 10m	25.0 km	+2,930 m / -2,930 m	Maximum physical grade (10/10); long knife-edge ridge with intense ups and downs to Hontaniyama (`本山`) / Iide Honzan. Commonly combined with Marumori Ridge as an advanced loop.

(Note: From the Fukushima side, the historic Kawairi / Mirokuzawa Course (川入・弥平四郎コース) from Kitakata is another popular 1N2D–2N3D route via Mikunidake Hut (三国岳避難小屋) and Kiritachi Hut (切合小屋).)

Detailed Guide to the Main Routes

1. Dainichisugi Course (`大日杉コース`) — The Shortest Route to Iide Honzan

Starting at Dainichisugi Goya (大日杉小屋, ~605 m) in Iide Town, Yamagata Prefecture, this is the most direct path to the main peak:

Dainichisugi Goya (大日杉小屋, 605 m) to Jizodake (地蔵山, 1,485 m) — ~3h 30m: Right from the trailhead, you tackle Zangezaka (ざんげ坂, "Repentance Slope"), a relentless root-and-rock climb fitted with fixed chains (鎖場), followed by Choizaka (長之助清水 vicinity) up to the junction below Jizodake.
Jizodake Junction to Kiritachi Hut (切合小屋, 1,750 m) — ~2h 15m: Follow the ridge over Mekkosayama (目洗沢) and across snow patches to Kiritachi Hut (切合小屋), where the Dainichisugi trail merges with the Kawairi trail from Fukushima.
Kiritachi Hut (切合小屋) to Mt. Iide Honzan (飯豊本山, 2,105 m) — ~2h 15m: Climb over Kusariyama (草履塚, 1,908 m), traverse the rocky 姥権現 (Ubagongen) and Gohiraki (御秘所, a short exposed rock traverse with fixed chains), pass Honzan Hut (本山小屋) and Iideyama Shrine, and walk another 10 minutes along the gentle summit plateau to the 2,105 m triangulation point of Mt. Iide Honzan.

2. Tengudaira: Marumori Ridge (`丸森尾根`) & Daigura Ridge (`ダイグラ尾根`)

Starting at Iide Sanso / Tengudaira Lodge (飯豊山荘・天狗平ロッジ, ~460 m) at the head of the Tamagawa River valley in Oguni Town:

Marumori Ridge (丸森尾根): Cross the Nukumidaira suspension bridge and climb steeply past Marumori Peak (丸森峰) and Jizodaira (地蔵平) to Kairagi Hut (梅花皮小屋, 1,890 m) at the saddle between Mt. Kitamata (北股岳, 2,025 m) and Mt. Kairagi (梅花皮岳, 1,910 m). From there, enjoy one of Japan's finest sky-ridge walks south over Mt. Eboshi (烏帽子岳, 2,018 m) and Onishi Hut (御西小屋) to Iide Honzan (and optionally a 3-hour round trip west to Mt. Dainichi (大日岳, 2,128 m), the highest point in the range).
Daigura Ridge (ダイグラ尾根): Cross the Kajikazawa suspension bridge (カジカ沢吊橋) and climb the long, exposed ridge over Hiyama (桧山) and Hokotate Peak (鉾立峰, 1,570 m) directly up to the steep eastern wall below Honzan Hut. Because there is no reliable water source on Daigura Ridge until you reach the upper snowmelt, carry at least 3.0–3.5 liters of water on hot summer days.

Unmanned Refuge Huts, Caretakers, and Water Sources

Unlike the Northern Japan Alps where full-service lodges serve hot meals and provide bedding, all upper-ridge huts in the Iide Range are unmanned refuge huts (無人避難小屋):

Hut Name	Location / Elevation	Type & Summer Caretaker	Cooperation Fee (`協力金`)	Water Source (`水場`) & Notes
Kiritachi Hut (`切合小屋`)	Between Kusariyama & Tanemakiyama (~1,750 m)	Unmanned refuge hut (caretaker resident Jul–Sep; sells drinks/light items when present, no meals/bedding)	~2,000 yen/night (tent ~1,000 yen)	Snowmelt spring ~3 min from hut (boil/filter late in season).
Honzan Hut (`本山小屋`)	Just below Iideyama Shrine (~2,060 m)	Unmanned refuge hut (caretaker resident in peak summer)	~2,000 yen/night	Spring ~5–10 min down slope (can run dry in late Aug/Sep—check beforehand).
Onishi Hut (`御西小屋`)	Saddle at Mt. Onishi (~2,000 m)	Unmanned refuge hut (rebuilt wooden cabin)	~2,000 yen/night	Snowmelt water ~10 min away (often dries up from late August onward).
Kairagi Hut (`梅花皮小屋`)	Saddle between Kitamata & Kairagi (~1,890 m)	Unmanned refuge hut (flush toilet using snowmelt in summer; tent site outside)	~2,000 yen/night (tent ~1,000 yen)	Famous cold spring (`梅花皮清水`) right below the hut—one of the most reliable water sources on the ridge.
賴母木小屋 (`Tanomogi Goya`)	Near Mt.eboshi / Kitamata north side (~1,670 m)	Unmanned refuge hut	~2,000 yen/night	Abundant spring right outside the hut.
Dainichisugi Goya (`大日杉小屋`)	Dainichisugi Trailhead (605 m, Iide Town)	Staffed trailhead lodge (reservation required; check Yamagata Mountain Portal)	Paid lodging (check current rates)	Running water, parking (~50 cars), flush toilets.
Iide Sanso (`飯豊山荘`)	Tengudaira Trailhead (460 m, Oguni Town)	Staffed trailhead inn & hot spring (open late May – early Nov; check Yamagata Mountain Portal)	Paid inn & day-use bath	Parking (~100 cars), hot spring bath, and adjacent Tengudaira Lodge.

Mandatory Overnight Gear for Mt. Iide Refuge Huts:

Sleeping bag (comfort rating around 0°C to 5°C in July/August, or -5°C in September/October) and sleeping pad
Stove, fuel, cookware, and all meals + emergency rations
Water filter or purification tablets (or extra fuel to boil water) because most ridge water sources come from snowmelt (雪渓の水)
6-point or 10-point crampons (軽アイゼン・チェーンスパイク) when crossing steep snow patches (石転び沢上部 or 切合〜草履塚) in July