Mt. Oasahidake (大朝日岳, 1,871 m), straddling Nishikawa, Oe and Oguni Towns in Yamagata Prefecture, is the principal peak of the Asahi range within Bandai-Asahi National Park — known in Kyūya Fukada’s “100 Famous Mountains of Japan” as “Asahi-dake” (the namesake of the Asahi mountain range).
Called the “Tōhoku Alps”, the Asahi range has the most extensive beech primeval forest in Tōhoku and famed Hime-sayuri lily fields (Lilium rubellum, early–mid July) along the ridge, with 360° panoramic summit views to Mt. Gassan, Mt. Chōkai, the Iide range and the Zaō range. The standard Kodera-kosen course and Asahi-kosen course are advanced ★★★★★ / 18 km / 1,750 m gain / 1-night 2-day plan with Oasahi Hut overnight recommended.
How to access the trailheads
- [Outbound] Tokyo / Osaka → Yamagata Station → Aterazawa Station (JR Yamagata Shinkansen + Sagae Line)
- [Round trip] Aterazawa Station ⇔ Kodera-kosen / Asahi-kosen (summer climbing bus / taxi)
- Kodera-kosen course, Oasahi Hut, suggested plans
Standard times (Kodera-kosen course, 1 night 2 days, advanced, ~12 hours)
Day 1 (~6 hours): Kodera-kosen (670 m) → (2:00) → Kodera-yama (1,500 m) → (1:30) → Ko-asahi-dake (1,648 m) → (1:00) → Gingyokusui → (1:30) → Oasahi Hut (1,820 m, below summit), overnight
Day 2 (~6 hours): Oasahi Hut → (0:30) → Mt. Oasahidake summit (1,871 m) → (5:30) → Kodera-kosen (return)
1. [Outbound] Tokyo / Osaka → Yamagata Station → Aterazawa Station (JR Yamagata Shinkansen + Sagae Line)
The Yamagata-side base for Mt. Oasahidake is Aterazawa Station (terminus of the JR Sagae Line). From Tokyo Station, JR Yamagata Shinkansen Tsubasa reaches Yamagata in about 2 h 40 min for ¥11,710; the JR Sagae Line then reaches Aterazawa in about 50 min for ¥510. From Osaka, ~5 h via Tokyo. From major cities, Yamagata Airport (direct flights from Tokyo / Osaka / Sapporo / Nagoya) + airport limo to Yamagata Station (~35 min, ¥1,000).
JR and airport access guide :
Tokyo Station → Yamagata Station : JR Yamagata Shinkansen Tsubasa about 2 h 40 min, ¥11,710 (reserved)
Yamagata Station → Aterazawa Station : JR Sagae Line about 50 min, ¥510
Osaka Station → Yamagata Station : JR via Tokyo about 5 h, ~¥18,000
Tokyo / Osaka → Yamagata Airport : direct flights (JAL/FDA), limo ~35 min, ¥1,000
Reference : JR East ｜ Yamagata Pref. Mt. Oasahidake guide
Inquiries : JR Yamagata Station ☎023-622-0322
2. [Round trip] Aterazawa Station ⇔ Kodera-kosen / Asahi-kosen (summer climbing bus / taxi)
From Aterazawa Station to the trailheads: Asahi-kosen (Nishikawa Town side) is reached by Asahi Climbing Bus in about 1 h 15 min, 1–2 runs/day in summer (2026 only open from Niigata side — confirm); Kodera-kosen (Oe Town side) is by taxi only, about 50 min for ~¥10,000. Oe Taxi (☎0237-62-2155) offers climber plans with drivers familiar with the Asahi range. Self-drive: ~30 min from Gassan IC or Nishikawa IC on the Yamagata Expressway.
Operating period : Asahi Climbing Bus summer (typically Jul–Sep, 2026 confirm), Kodera-kosen by taxi year round
Travel time : Aterazawa → Asahi-kosen about 1 h 15 min (bus) / Aterazawa → Kodera-kosen about 50 min (taxi)
Fare : Asahi Climbing Bus ~¥1,500, taxi ~¥10,000 (Kodera-kosen)
Frequency : Asahi Climbing Bus 1–2 runs/day (summer only)
Aterazawa Station → Asahi-kosen (Asahi Climbing Bus, summer-only, hiker excerpt — 2026 confirm)
| Aterazawa Station dep. | Asahi-kosen arr. |
|---|---|
| around 9:00 (morning) | around 10:15 |
| around 14:00 (afternoon, select days) | around 15:15 |
Asahi-kosen → Aterazawa Station (Asahi Climbing Bus, return, summer-only)
| Asahi-kosen dep. | Aterazawa Station arr. |
|---|---|
| around 10:30 | around 11:45 |
| around 15:30 (last) | around 16:45 |
Note : The 2026 road repair on the Asahi-kosen approach means operation and access may be restricted — always confirm with Asahi-kosen official or Asahi-kosen Naturalist Lodge ☎0237-67-2860. The Kodera-kosen route is stable. After descending, bathe at Oisawa Onsen “Yuttari-kan” (¥300).
Reference : Asahi-kosen access ｜ Oe Taxi Asahi range climbing
Inquiries : Asahi-kosen Naturalist Lodge ☎0237-67-2860 / Kodera-kosen Choyo-kan ☎0237-67-2226 / Oe Taxi ☎0237-62-2155
3. Kodera-kosen course, Oasahi Hut, suggested plans
About Mt. Oasahidake
The principal peak of the Asahi range (1,871 m) in Yamagata Prefecture, within Bandai-Asahi National Park. Selected by Fukada as “Asahi-dake” in his 100 Famous Mountains (the namesake peak of the entire Asahi range). Called the “Tōhoku Alps”, it features the longest ridges in Tōhoku, the most extensive beech primeval forest in Tōhoku, the famed Hime-sayuri lily ridge fields (early–mid July, endangered species), and a 360° summit panorama over Mt. Gassan, Mt. Chōkai, the Iide range and the Zaō range.
Trail summary (3 main courses)
- Kodera-kosen course (Oe Town side, standard, advanced, ~12 h, 1 night 2 days): Kodera-kosen → Kodera-yama → Ko-asahi-dake → Oasahi Hut → summit out-and-back, through beech primeval forest
- Asahi-kosen course (Nishikawa Town side, advanced, ~12 h, 1 night 2 days, 2026: only open from Niigata side): Asahi-kosen → Torihara-yama → Ko-asahi-dake → Oasahi-dake
- Ito-dake traverse (advanced, 2 nights 3 days): full Asahi range traverse
Huts and hot springs (2026 information)
– Oasahi Hut (below summit, 1,820 m, no phone): for-fee (cooperation fee ~¥2,500), manager resident Jul–Sep, bring bedding and food, toilet, capacity ~80. Outside the staffed period, usable but unmanaged
– Asahi-kosen Naturalist Lodge (trailhead, ☎0237-67-2860): lodging ¥9,500+, self-cooking ¥6,000+, best climbing base (2026 access by road repair — confirm)
– Kodera-kosen Choyo-kan (trailhead, ☎0237-67-2226): lodging ¥10,000+, climbing base
– Oisawa Onsen “Yuttari-kan” (¥300, after descent)
Climbing season / flowers: mid-June to mid-October. Early–mid July: Hime-sayuri lily fields (endangered, ridge), Hakusan-ichige, Nikkō-kisuge. Late September – October: autumn colours and beech yellow. Residual snow on the ridge and around Gingyokusui until early June.
Cautions
– 2026 Asahi-kosen access road under repair: use the Kodera-kosen route or confirm with Asahi-kosen
– 1 night 2 days (effectively required): 12-hour course, not a day hike, Oasahi Hut overnight
– Limited water: Gingyokusui and Kingyokusui (near Oasahi Hut) only — carry at least 2 L
– Bear sightings common: carry bells and pepper spray, watch for scat
– No picking Hime-sayuri: MOE Red List, Yamagata Prefecture protected
Emergency contacts and inquiries
- Nishikawa Town Hall (Asahi-kosen side): ☎0237-74-2111 / Oe Town Hall (Kodera-kosen side): ☎0237-62-2111
- Oguni Town Hall (Iwa-i-bachi-yama, south side): ☎0238-62-2111
- Sagae Police Station (climbing plan, mountain rescue): ☎0237-86-0110
- Asahi-kosen Naturalist Lodge (lodging): ☎0237-67-2860 / Kodera-kosen Choyo-kan: ☎0237-67-2226
- Oe Taxi (Kodera-kosen transfer): ☎0237-62-2155
Suggested plan (Kodera-kosen course 1 night 2 days, recommended)
- Day 1: Tokyo 6:00 → Yamagata 9:00 → Aterazawa 10:00 → Oe Taxi → Kodera-kosen 11:00 → Kodera-yama 13:00 → Ko-asahi-dake 14:30 → Oasahi Hut 17:00 overnight
- Day 2: early summit 6:00 (sunrise, 360° view) → descend → Kodera-kosen 12:00 → taxi → Aterazawa 13:00 → Oisawa Onsen bath → return
- For the Hime-sayuri lily bloom (early–mid July), book Oasahi Hut a month in advance
Reference : Asahi-kosen official ｜ Yamagata Pref. Mt. Oasahidake guide
Photo by Wikimedia Commons
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