Akita · Tamagawa Onsen
Shin-Tamagawa Onsen
新玉川温泉
A modern cure-bath inn fed by Tamagawa Onsen, Japan's most acidic spring at pH 1.2. The hiba-cypress bathhouse lines up 15 tubs — 100% source, 50% diluted, mildly acidic and more — so you can choose by condition. Day use 10:00–15:00, ¥1,000 (revised April 2026). An indoor stone-slab bath (¥800) is also available, and unlike the original Tamagawa it stays open all winter for snowbound soaking. About 70 min by bus from Tazawako Station.
- Price (adult)
- ¥1,000
- Hours
- 10:00–15:00 (last entry 14:30)
- Closed
- Open daily (occasional closures)
- Access
- About 70 min by Ugo Kotsu bus from JR Tazawako Station to Shin-Tamagawa Onsen; 110 min by car from Morioka IC
- Water type
- Acidic spring
- Tattoos
- Ask ahead
- Admission
- Day bathing: adults ¥1,000 / children ¥500 (revised April 2026). Towels sold ¥200. The indoor bedrock bath (¥800, reservation) is for overnight guests only. 'Bathing briefings' are held on Fri/Sat/Sun evenings
- Baths
- Fifteen kinds of tub in the gender-separated bathhouse — 100% source water, a 50% diluted pool, tepid bath, lie-down bath, cascade, steam box, thermal beds, steam room, drinking fountain and more. More tubs than the original Tamagawa Onsen, in a newer, barrier-free building. Rotenburo and private bath available
- Water
- Acidic, CO₂- and iron(II)-bearing chloride spring. The 'Obuki' source is 97.3°C with a pH of 1.13 — Japan's most acidic spring, hydrochloric acid its main component, and the largest single-vent flow in the country (about 9,000 L/min). Total minerals 5.5 g/kg, iron 111 mg, metasilicic acid 448 mg. Piped about 1 km from the same source as Tamagawa Onsen
- Parking & access
- Free parking. About 70 min from Tazawako Station on the Ugo Kotsu Hachimantai Line bus to 'Shin-Tamagawa Onsen', right at the stop (in winter buses run only between Tazawako Station and Shin-Tamagawa). About 60 min from Kazuno-Hachimantai IC on the Tohoku Expressway via Route 341. Free shuttle from Tazawako Station for overnight guests (reserve)
- Phone
- 0187-58-3100
- Official site
- shintamagawa.jp ↗
- Open in Google Maps
- Google Maps ↗
Essentials
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Why go
- Japan's most acidic spring, pH 1.2
- 15 tubs graded by source strength
- Open in winter (the original inn closes)
Japan's most acidic spring, pH 1.1, made barrier-free — a 15-tub curative hotel sharing Tamagawa's 'Obuki' source
Shin-Tamagawa Onsen opened in 1998 about 1 km down Route 341 from Tamagawa Onsen in the Hachimantai mountains of Semboku, Akita, as a sister facility piping in water from the globally rare 'Obuki' source. Obuki gushes 97.3°C water at roughly 9,000 litres a minute from a single vent — the largest flow in Japan — at pH 1.13, the country's most acidic spring, with hydrochloric acid as its main component; three minutes in and your skin tingles, and any cut screams. To tame that intensity, the gender-separated bathhouse lines up fifteen kinds of tub — 100% source water, a 50% dilution, tepid, lie-down and cascade baths, steam boxes, thermal beds and more — and overnight guests get an indoor bedrock bath, a bathing-advice room and evening 'bathing briefings' from Friday to Sunday; most people come to convalesce. Unlike the ageing therapy lodges of the original Tamagawa, the building is new and barrier-free, easy for elderly visitors and families, and — decisively — it stays open in winter, when the original closes. Day bathing runs 10:00–15:00 for ¥1,000. Come knowing this is not a leisure onsen but one where you confront your own body.
Tips & notes
① Start with under three minutes in the 100% tub; keep it away from eyes, mucous membranes, cuts and freshly shaved skin. Rinse with fresh water afterwards and remove silver or metal jewellery beforehand (it tarnishes). Contact-lens wearers: keep water out of your eyes. ② The acid degrades towels and swimwear — bring old ones. ③ Day visitors cannot use the bedrock bath; reception closes 14:30. ④ Busy with therapy guests in high summer and on winter weekends. ⑤ If pregnant, hypertensive or with heart disease, skip the 100% tub for the diluted or tepid pools. ⑥ Mobile signal is weak in the mountains; in winter Route 341 is open only on the Tazawako side (the Hachimantai side closes).
Getting there
From Tazawako Station on the Akita Shinkansen (about 3 h from Tokyo), the Ugo Kotsu Hachimantai Line bus takes about 70 min to 'Shin-Tamagawa Onsen', right at the stop. Only 3–4 buses a day, and in winter (mid-Nov to mid-Apr) they run solely between Tazawako Station and Shin-Tamagawa — check the timetable. Overnight guests get a free shuttle from Tazawako Station (reserve). By car, about 60 min south on Route 341 from Kazuno-Hachimantai IC on the Tohoku Expressway, or about 50 min from Tazawako Station. The winter base for a Hachimantai therapy circuit with Tamagawa Onsen (15 min on foot, summer only), Fuke-no-yu and Goshogake.
Before you go
- No official tattoo policy is published — ask at reception.
- Strongly acidic water — rinse off afterwards, avoid long soaks, and remove silver jewellery.
- Ryokan day-use hours are limited and may be suspended in peak season — phone the same morning.
- Last entry is 30–60 minutes before closing.
Features
Sauna & wellness
Price
Who with
Convenience
Mood & scenery
Amenities
✔ Verified operating: 2026-09 Operating status and rates cross-checked against the official site and onsen guides (full source notes in Japanese on the JA page)
Prices and hours change. Check official sources before visiting.
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