Yamanashi Prefecture, nestled among the peaks of the Southern Alps and Mt. Fuji, is a land of remarkable geological diversity. The Fossa Magna fault system and surrounding mountain ranges give rise to a wealth of hot springs across the prefecture — from historic spa towns linked to the legendary warlord Takeda Shingen, to remote single-inn retreats, to rare radium springs and iron-rich rustic baths. This guide introduces 10 of Yamanashi's most compelling secret hot springs (秘湯, hitoyu), covering a range of spring types and access levels.
1. Narada Onsen Shiranekan — Nara District, Hayakawa Town
Deep in the Southern Alps, near the point where Yamanashi, Shizuoka, and Nagano prefectures meet, lies Narada Onsen — roughly two hours by car from Kofu via Route 37. Long referred to as the "Spring of Seven Mysteries," this hot spring is known for its striking color variations: the water can appear transparent, emerald green, or milky white depending on the season and weather.
Shiranekan is the primary facility at Narada Onsen, having opened in 1962. The spring is classified as a sulfur-containing sodium chloride spring with an alkaline pH of 9.1, producing a notably silky texture on the skin. The spring ranked third nationally in the "Beautiful Skin" category at the 2016 Onsen Grand Prix. At present, overnight stays are suspended and only day-use bathing is available. Visitors should confirm the current operating status before planning a trip.
Quality
含硫黄－ナトリウム－塩化物泉（硫化水素型）
Temp
42℃ to 48℃
Flow
Natural Source Flow
pH
pH 9.1
0714
AcidicNeutralAlkaline
Use
Stay N/A/Day Trip OK
Fee
Adult 1000JPY/Child 500JPY
Hours
| Mon | Tue | Wed | Thu | Fri | Sat | Sun | Hol | |
|---|---|---|---|---|---|---|---|---|
| 10:30 - 16:00 | ◯ | ◯ | ◯ | ◯ | ◯ | 10:30-17:00 | 10:30-17:00 | 10:30-17:00 |
Founded in 705 CE during the Asuka period, Keiunkan is certified by Guinness World Records as the world's oldest hotel. Located in the mountains of Hayakawa Town, the inn has operated continuously for over 1,300 years. Despite its extraordinary heritage, it remains a functioning hot spring inn accessible to visitors.
The spring is a sodium-calcium sulfate chloride type with a pH of 9.36. With a combined output of 2,030 liters per minute from both artesian and drilled sources, the inn uses undiluted source water throughout the entire facility — including showers. Six different bath types are available, all using 100% source water with no heating or dilution. The inn underwent renovation in late 2025 to early 2026; visitors should check current availability before booking.
Quality
ナトリウム－塩化物・硫酸塩泉
Temp
42℃ to 52℃
Flow
Natural Source Flow
pH
pH 9.4
0714
AcidicNeutralAlkaline
Use
Stay OK/Day Trip N/A
Book your stay
Located near the trailhead for Daibosatsu Pass in Koshu City, Sakkeishi Onsen takes its name from a legend claiming that over 1,200 years ago, a lightning strike split a rock and caused the spring to emerge from the fissure. Despite being relatively accessible from Kofu, the surrounding forested terrain gives the spa a genuinely secluded feel.
Unposo is a historic single-inn establishment dating to the Meiji era. The spring is a highly alkaline simple spring (単純アルカリ泉) with a pH of 9.9 and a source temperature of just 26.6°C. Guests can enjoy alternating baths between heated pools and the cold spring water. The outdoor bath features large natural rock formations. Unposo is a registered member of the Japan Secret Hot Spring Association (日本秘湯を守る会).
Quality
アルカリ性単純温泉
Temp
26℃ to 42℃
Flow
Natural Source Flow
pH
pH 9.9
0714
AcidicNeutralAlkaline
Use
Stay OK/Day Trip OK
Fee
Adult 500JPY/Child 400JPY
Hours
| Mon | Tue | Wed | Thu | Fri | Sat | Sun | Hol | |
|---|---|---|---|---|---|---|---|---|
| 10:00 - 13:00 | ◯ | ◯ | ◯ | ◯ | ◯ | × | × | × |
Book your stay
Hidden in the forested mountains of Fujikawa Town, Akaishi Onsen is a rustic single-inn retreat best known for its reddish-brown iron-rich spring water. The source temperature is a cold 12.6°C, classifying it as a cold mineral spring (冷鉱泉). The distinctive tinted water leaves a strong impression on first-time visitors.
Four outdoor baths are available at different temperatures, allowing guests to move between warmer and cooler pools. Surrounded by deciduous forest, the experience combines forest bathing with traditional thermal soaking. Akaishi Onsen is a member of the Japan Secret Hot Spring Association, and the meals — featuring local mountain vegetables and river fish — are also well-regarded.
Quality
単純酸性泉
Temp
12℃ to 42℃
Flow
循環濾過
pH
pH 2.2
0714
AcidicNeutralAlkaline
Use
Stay OK/Day Trip OK
Fee
Adult 800JPY/Child 500JPY
Hours
| Mon | Tue | Wed | Thu | Fri | Sat | Sun | Hol | |
|---|---|---|---|---|---|---|---|---|
| 10:00 - 16:00 | × | × | × | × | × | ◯ | ◯ | ◯ |
Book your stay
Sanwaso is situated in the Ashiyasu Onsen district of Minami-Alps City, a mountain spa area that also serves as a base for climbing the Southern Alps. Founded in 1869 (Meiji 2), it is regarded as the oldest inn in the Ashiyasu area and continues to operate as a family-run establishment.
The spring is a simple alkaline spring at 42.6°C — warm enough to use at natural temperature without heating, making it a true unblended flow-through bath. The inn also accommodates guests traveling with dogs; a private bath where owners can bathe together with their pets is available, which is a notable rarity among Japanese hot spring inns.
Quality
アルカリ性単純温泉
Temp
42℃ to 43℃
Flow
Natural Source Flow
pH
pH 9.6
0714
AcidicNeutralAlkaline
Use
Stay OK/Day Trip OK
Fee
Adult 1000JPY/Child 500JPY
Hours
| Mon | Tue | Wed | Thu | Fri | Sat | Sun | Hol | |
|---|---|---|---|---|---|---|---|---|
| 11:00 - 17:00 | ◯ | ◯ | ◯ | ◯ | ◯ | ◯ | ◯ | ◯ |
One of the most historically significant hot springs in Yamanashi, Shimobe Onsen has approximately 1,300 years of recorded history. It is widely known as a representative example of Shingen's Hidden Baths (信玄の隠し湯), referring to the legend that warlord Takeda Shingen used this and other springs to treat wounded soldiers. The old spa town atmosphere is still palpable in Shimobe, making it a rare surviving example of a traditional Japanese hot spring district.
The area has multiple sources: the traditional cold spring at 30–32°C, and a higher-temperature drilled source (known as Shimobe Okuno-yu) that produces water at 51°C with a pH of 9.3. The spring has historically been credited with efficacy for bone fractures, bruises, and cuts, and the water is also suitable for drinking. Multiple ryokan in the area offer flow-through bathing.
Quality
アルカリ性単純温泉
Temp
30℃ to 51℃
Flow
Natural Source Flow
pH
pH 9.3
0714
AcidicNeutralAlkaline
Use
Stay OK/Day Trip OK
Fee
Adult 500JPY/Child 300JPY
Hours
| Mon | Tue | Wed | Thu | Fri | Sat | Sun | Hol | |
|---|---|---|---|---|---|---|---|---|
| 10:00 - 15:00 | ◯ | ◯ | ◯ | ◯ | ◯ | ◯ | ◯ | ◯ |
Book your stay
At an elevation of approximately 1,050 meters in the mountains of Hokuto City, Masutomi Radium Onsen has been attracting visitors seeking therapeutic bathing for generations. The spring contains radium levels that exceed international standards, and has historically been called "the spring that cures all ailments." The source temperature is a cold 20.1°C.
Furoukaku (the inn) is known for its signature rock bath, where radium spring water bubbles up directly through the rock floor — a striking visual unique to this location. A dedicated room for inhaling radium steam is also available, as is drinking the spring water. Bathing alternately between the cold radium pool and a heated bath is the recommended method. Some facilities have a certified hot spring therapist on staff.
Quality
含放射能
Temp
17℃ to 21℃
Flow
Natural Source Flow
pH
pH 6.3
0714
AcidicNeutralAlkaline
Use
Stay OK/Day Trip OK
Fee
Adult 1000JPY/Child ---JPY
Hours
| Mon | Tue | Wed | Thu | Fri | Sat | Sun | Hol | |
|---|---|---|---|---|---|---|---|---|
| 12:30 - 14:00 | ◯ | × | ◯ | ◯ | ◯ | ◯ | ◯ | ◯ |
Book your stay
8. Iwashita Onsen Ryokan — Kamiiwashita, Yamanashi City
Located in Yamanashi City, Iwashita Onsen Ryokan offers a relatively accessible introduction to cold-mineral-spring bathing. Despite its proximity to the Kofu Basin, the spring — a simple alkaline type at 26°C and pH 9.0 — has a strong individual character befitting its reputation as a local hidden bath.
The inn features a cold spring pool in the basement that uses undiluted source water, alongside a heated pool on an upper floor. Alternating between the two is the traditional bathing method, said to warm the body from its core through the contrast of temperatures. Historical connections to the Takeda clan have also been noted in relation to this spring. Day-use admission is a modest 500 yen.
- Spring type: Simple alkaline spring
- Source temperature: 26°C, pH 9.0
- Day use: Available (500 yen)
- Overnight stay: Available
- Special features: Cold spring pool in basement; alternate bathing recommended
9. Kawaura Onsen Yamagatakan — Yamanashi City
Kawaura Onsen Yamagatakan is a historic hot spring inn located along the upper reaches of the Fuefuki River gorge in Mitomi-Kawaura, Yamanashi City, Yamanashi Prefecture. In 1561, the renowned warlord Takeda Shingen ordered Yamagata Masakage, one of the Four Guardians of the Takeda clan, to develop this hot spring, making it the only documented example of a spring developed by Shingen. The inn has been passed down through fifteen generations of the same family since its founding. It features two spring sources: Yamagatakan No. 1 (41.2 degrees Celsius) and Yamagatakan No. 2 (43.2 degrees Celsius), both delivered as 100% free-flowing natural spring water without heating, dilution, or recirculation. The flow rate is an impressive 1,144 to 1,250 liters per minute, ranking among the highest in Japan. The water is a highly alkaline simple hot spring with a pH of 9.6, renowned as a beauty skin spring. The inn offers multiple bathing facilities including the Shingen Rock Bath (mixed bathing with women-only hours), Fuefuki Senryu Miyabi-no-Yu, Yakushi-no-Yu, and Seseragi-no-Yu, with open-air baths crafted from massive Japanese cypress logs overlooking the mountain stream and its seasonal scenery. The main baths are available 24 hours.
Quality
アルカリ性単純温泉
Temp
41℃ to 43℃
Flow
Natural Source Flow
pH
pH 9.6
0714
AcidicNeutralAlkaline
Use
Stay OK/Day Trip OK
Fee
Adult 1500JPY/Child 800JPY
Hours
| Mon | Tue | Wed | Thu | Fri | Sat | Sun | Hol | |
|---|---|---|---|---|---|---|---|---|
| 00:00 - 24:00 | ◯ | ◯ | ◯ | ◯ | ◯ | ◯ | ◯ | ◯ |
Book your stay
Also in the Ashiyasu Onsen district of Minami-Alps City, Iwazono-kan is a quiet inn near the bus terminal for routes into the Northern Southern Alps. It serves both leisure visitors and mountaineers using the area as a staging point for the Kitazawa Pass trailhead.
The spring is a sodium-calcium sulfate chloride type, known for its potential benefits for muscle pain, joint discomfort, and general fatigue recovery. The inn uses 100% source water in a flow-through system without dilution or additional heating. The outdoor bath looks out onto the surrounding mountain terrain. For visitors seeking an unhurried stay near pristine alpine wilderness, this inn offers a quietly rewarding experience.
Quality
ナトリウム－硫酸塩・塩化物泉
Temp
43℃ to 44℃
Flow
Natural Source Flow
pH
pH 9.3
0714
AcidicNeutralAlkaline
Use
Stay OK/Day Trip OK
Fee
Adult 1000JPY/Child ---JPY
Hours
| Mon | Tue | Wed | Thu | Fri | Sat | Sun | Hol | |
|---|---|---|---|---|---|---|---|---|
| 10:00 - 15:30 | ◯ | ◯ | ◯ | ◯ | ◯ | ◯ | ◯ | ◯ |
Book your stay
Closing Notes
Yamanashi's hot springs range from springs with over a millennium of recorded history to iron-rich rustic baths requiring a winding mountain drive to reach. Whether you seek the curiosity of color-changing water, the novelty of the world's oldest inn, the therapeutic claims of a radium spring, or the simplicity of a cold mineral bath in a remote forest, Yamanashi offers a hot spring experience unlike any other region in Japan. Always verify current operating hours and access conditions directly with each facility before visiting.
The information in this article reflects research conducted at the time of writing. There may be inaccuracies or changes. Please confirm the latest details via each facility's official website or by contacting them directly before your visit.
