Ryokan (inn) · Seasonal
Tamagawa Onsen (toji inn with self-catering wing)
- Day-use bathing
- Yes
- Fee
- ¥1,000checked 2026-10-09
- Hours
- 日帰り入浴 10:00–15:00(最終受付14:30)/宿泊者の大浴場 3:00–24:00checked 2026-10-09
Photo information
Save to passport
Official classification
Spring type (therapeutic classes)
Official spring-type name (as recorded)Acidic chloride spring (acidic, hypertonic); the inn describes it as strongly acidic water, pH 1.2, with hydrochloric acid as the main component
- Source temperature
- 98°C
- pH
- 1.05
- Flow rate
- 9,000 L/min
- Radon
- Present
Appearance & feel
Water colour · Feel
Yunohana (mineral flakes) · Yes
Colour and feel are listed only where a source states them. They vary by day and by bath.
What makes it special
At pH 1.2 and roughly 9,000 litres a minute from a single vent, Japan's most acidic hot spring pours out of a steaming valley.
Why?
The inn's site describes the Obuki source as 98°C, pH 1.2 and about 9,000 litres a minute from one vent, both national records.[1]
Facilities in this area
Facilities come from the register (Wikipedia, OpenStreetMap, official sites). Those marked "natural spring unconfirmed" are listed on the basis of their name only.
Getting there
Reachable by public transport
From Tazawako Station on the Akita Shinkansen, an Ugo Kotsu bus takes about 1 hour 20 minutes (summer season only; in 2026 until mid-November). From Kazuno-Hanawa on the JR Hanawa Line a Shuhoku bus takes about 1 hour 15 minutes. By car it is about 1.5 hours from the Morioka interchange on Routes 46 and 341; Route 341 closes 19:00–8:00 just after it reopens in spring and just before it shuts in autumn.
- Getting there
- Tazawako Station (Akita Shinkansen / JR Tazawako Line) · 80
- Through the year
- Route 341 closes for winter; Tamagawa Onsen itself closes (open late April to late November) and the buses run only in the summer season
- Checked
- 2026-10-09
About the water
A strongly acidic water, pH 1.2, whose main acid is hydrochloric; it is regarded as the most acidic hot spring in Japan. The 100%-source tub is kept lukewarm because it stings, and the inn recommends alternating with 50%-diluted and mild-acid tubs to let your skin adjust. Drinking is allowed only in small amounts diluted 38 times. The water carries trace radioactivity (radium); the inn speaks of a hoped-for low-dose hormesis effect, which is not medically established. Downstream the acid once killed rice paddies and fish, earning the name Tamagawa poison water, and since 1972 it has been neutralised with limestone before it reaches the river.
Indications (as posted on the analysis)
The inn lists nervous-system complaints including rheumatism, circulatory complaints, skin disease and fatigue recovery under benefits; the formal indications from the analysis sheet were not seen
Indications are an official statement based on the water analysis, not a guarantee of treatment. They are kept separate from opinions.
| Source | Source temperature | pH | Radon | Checked |
|---|---|---|---|---|
| Obuki | 98 | 1.2 | Unconfirmed | no check date |
Three things not to miss
Photo information
Obuki and the nature trail
Above the inn, on the roughly 30-minute loop trail A river of hot water runs from Obuki, where 98°C water erupts, and steam vents hiss across the slope. A stone-paved loop path circles it through old-growth beech and fir.
Nowhere else in Japan can you stand beside this much hot water erupting from the ground. The trail is for the snow-free season; the inn itself is open from late April to late November.[1][2]
Photo information
Natural bedrock bathing
The warm rock beside the trail, partly under tents You lay a straw mat on rock warmed by the earth, pull a blanket over yourself and lie there for about 40 minutes, turning now and then because some spots reach 40–50°C. Nothing is rented; bring your own mat and blanket.
This is where Japan's bedrock-bathing (ganban-yoku) tradition is said to have begun. After a fatal avalanche in 2012 the ground is closed in winter.[1][2]
Eleven kinds of bath, and a wing where you cook
The inn's main bathhouse and self-catering wing The hiba-cypress bathhouse has eleven tubs: 100% and 50% source water, a mild-acid pool, a tepid pool, a box steam bath, a waterfall massage and more. The self-catering wing's small tatami rooms come with a fridge and kettle for long stays.
The bathhouse is built around easing a newcomer into harsh water, and a nurse-staffed consultation room guides first-time toji guests.[1][3]
The story
From the deer's spring to Tamagawa
When a local hunter found the spring in 1680, a deer was bathing its wounds there, so it was called Shika-no-yu, the deer's bath. It stayed a remote cure spot until Seki Naoemon, who took the cure here in 1929, bought the rights; in 1934 a newspaper writer renamed it Tamagawa Onsen. A road and bus route arrived in 1950, and the sister inn Shin-Tamagawa opened in 1998.[2]
Hokutolite and bedrock bathing
In the streambed below Obuki a mineral called hokutolite forms: barite containing lead with traces of radium, known only here and at Beitou in Taiwan. It is a Special Natural Monument and may not be collected. Lying on the warm rock, soaking up heat and faint radiation at once, grew into a distinctively Japanese form of toji here. Since an avalanche near the bathing ground in February 2012, it has closed every winter.[2][1]
Turning poison into medicine
The pH 1.2 water once poisoned paddies and killed fish downstream, and when it was diverted into Lake Tazawa the lake's fish died out; since 1972 limestone beds have neutralised it. The inn has built dilution into its bathhouse, and with eleven tubs and a nurse-staffed consultation room supports guests who stay for weeks. It makes no official claim that the water cures serious disease.[2][1][3]
Going solo
Easy for solo travellersYes
Weekend / peak restrictionsUnconfirmed
Where to eat dinnerThe ryokan wing serves buffet meals; the self-catering wing cooks for itself. There are no shops nearby; the nearest convenience store is about 20 minutes by car
Private bathYes
checked 2026-10-09
Through the year
Recommended months
JanFebMarAprMayJunJulAugSepOctNovDec
Months open
JanFebMarAprMayJunJulAugSepOctNovDec
"Recommended" and "open" are recorded separately. Check the season for seasonal springs.
Apr · Nov — Around opening (late April) and closing (late November) Route 341 is shut overnight. The footbath runs 16 Apr–15 Nov
Jun · Jul · Aug · Sep · Oct — Season for the nature trail and bedrock bathing. In 2026 the inn asks visitors to carry bear bells and walk in groups because of bear activity
Dec · Jan · Feb · Mar — Tamagawa Onsen is closed; the year-round Shin-Tamagawa Onsen is the alternative
Food, culture & experiences
Shin-Tamagawa Onsen
The sister inn, opened in 1998, piped from the same source and open all year[1][2]
A few minutes by car from Tamagawa (distance not confirmed)Toji consultation room with nurses
Nurses advise first-time toji guests on how to bathe. There is no doctor and no medical treatment[1][2]
In the innLake Tazawa
Japan's deepest lake; the bus from Tazawako Station passes along its shore[2]
On the 80-minute bus route from Tazawako StationEditors' guide
For a day visit, the bathhouse is open 10:00–15:00; start in a 50% tub and move to 100% once your skin is used to it. The nature trail takes half an hour; for bedrock bathing bring a mat, a blanket and a change of clothes. To stay, a single room in the self-catering wing is the most authentic toji experience. The inn closes in winter, when Shin-Tamagawa takes over.
The "editors' guide" above is written by the editors from sources; it is not a visitor's opinion.
Photo gallery
Visitor reviews
No reviews yet. While the review platform is being prepared, we do not display fictional reviews or ratings.
Review posting is in preparation, with visit date, facility, comments on water, scenery and access, photos, language and reporting.
Overview
Tamagawa Hot Spring (玉川温泉, Tamagawa onsen) is a hot spring located in the city of Semboku, Akita in northern Japan.
This overview is based on the lead section of the English Wikipedia article (CC BY-SA 4.0). View original page
Unconfirmed & notes
- The 1680 discovery, hokutolite, the poison-water history and the 80-minute bus time are from Wikipedia (CC BY-SA)
- Formal classification as a radioactive spring and radon values are unconfirmed
- Room rates, exact 2026 opening and closing dates and bus frequency were not confirmed
- Whether tubs are free-flowing or recirculated is not posted online; only the 100%/50% source ratios are stated
Sources
- 【公式】玉川温泉(トップ・天然岩盤浴・アクセス)株式会社玉川温泉 · 2026-10-09
- 玉川温泉 (秋田県) - Wikipedia(日本語版)Wikipedia · 2026-10-09
- 温泉(大浴場・貸切浴場・日帰り入浴) | 玉川温泉株式会社玉川温泉 · 2026-10-09
- 温泉アトラス台帳 areas.json(湯の花の記録はWikipedia由来)Wikipedia · 2026-10-09
- 客室 | 玉川温泉株式会社玉川温泉 · 2026-10-09
Register sources
- 玉川温泉 (秋田県) - Wikipedia(日本語版)Wikipedia · CC BY-SA 4.0 · 2026-10-09
- Wikidata Q7680539Wikidata · CC0 · 2026-10-09
Data status
Name & locationPublishedCoordinatesPublishedSpring typePublishedPhotosPublishedFacilitiesPublishedVisiting info (dated)PublishedEditorial articlePublished
Updated 2026-10-09
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