Official classification
Official spring-type name (as recorded)Acidic sulfur spring (hydrogen-sulfide type); the association and Nisshinkan both say 'acidic sulfur spring'
Appearance & feel
Colour and feel are listed only where a source states them. They vary by day and by bath.
What makes it special
At 1,800 metres, 5.4 million litres of sulfur water a day. Thin air, deep snow, and a milky bath in the middle of it.
Facilities come from the register (Wikipedia, OpenStreetMap, official sites). Those marked "natural spring unconfirmed" are listed on the basis of their name only.
| Type | Gender | Source | Bath temperature | Free-flowing | Added water | Heated | Recirculated | Disinfected |
|---|---|---|---|---|---|---|---|---|
| Open-air bath | Separate | Unconfirmed | Unconfirmed | Unconfirmed[3] | Unconfirmed[3] | Unconfirmed[3] | Unconfirmed[3] | Unconfirmed[3] |
| Indoor bath | Separate | Unconfirmed | Unconfirmed | Unconfirmed[3] | Unconfirmed[3] | Unconfirmed[3] | Unconfirmed[3] | Unconfirmed[3] |
From Manza-Kazawaguchi Station on the JR Agatsuma Line, Seibu Kanko bus about 40 minutes. From Karuizawa (Hokuriku Shinkansen) Seibu buses take about 90 minutes via Manza-Kazawaguchi. Nisshinkan runs guest shuttles from Karuizawa (about 110 min) and Naganohara-Kusatsuguchi (about 55 min), booking required.
Manza's water is an acidic sulfur spring rich in hydrogen sulfide: milky or yellowish, with sulfur hanging in the air. Wikipedia credits it with the highest sulfur content in Japan, a flow of 3,750 litres a minute and sources at about 80 °C; the association counts about 20 sources and 5.4 million litres a day. Inns draw on different sources and name their tubs after them, 'Nigayu' (bitter bath), 'Ubayu' and so on. At 1,800 m, long soaks are hard on the body, so keep them short. Per-source temperature and pH could not be confirmed on official notices.
| Source | Source temperature | pH | Radon | Checked |
|---|---|---|---|---|
| Manza Onsen (about 20 sources) | Unconfirmed | Unconfirmed | Unconfirmed | no check date |
At the inns (e.g. Nisshinkan's Gokuraku-yu) Acidic sulfur water, milky white or yellowish. Each inn has open-air baths; Nisshinkan's Gokuraku-yu reopened on 1 August 2026 after reinforcement work.
Manza is one of the highest onsen in Japan reachable by car all year. The view of mountains and snow from a 1,800 m bath, with sulfur in the air, is hard to find anywhere else.[2][3]
Edge of the resort A field of vents giving off steam and hydrogen sulfide, Manza's trademark; the source area looks like the Japanese idea of hell.
Here you can see that the water's source is a volcano. The venting has weakened since about 2012. Beware of volcanic gas.[2]
Manza Onsen Nisshinkan An inn that takes day bathers and runs 3–6-night 'new toji' therapeutic-stay plans with morning exercise and wellness programmes. Shuttles from Karuizawa and Naganohara-Kusatsuguchi stations (reservation required).
Nisshinkan carries Manza's pre-war toji tradition into the present. Its day-use fee and hours could not be read on the official site, so check before visiting.[3][4][2]
Manza lies inside Joshin'etsu Kogen National Park at 1,800 m on the flank of Mt Kusatsu-Shirane, and with Nigorigo in Gifu is counted as the highest onsen in Japan reachable by private car all year. Nobody knows when the spring was first used; Yayoi-period pottery has been found nearby, and warriors came to bathe in the sixteenth century. It remained a modest toji spot through the Edo period and only took off after the war, when Seibu Group resort development brought proper roads.[2][3]
The water is an acidic sulfur spring of the hydrogen-sulfide type, milky white or yellowish. Wikipedia gives it the highest sulfur content in Japan, a flow of 3,750 litres a minute and a source temperature of about 80 °C; the association counts about 20 sources and 5.4 million litres a day. Hot water seeps up all along the riverbed, and the source area is wrapped in steam and the smell of sulfur. At the edge of the resort the Karabuki vents blow steam and hydrogen sulfide, Manza's signature sight.[2][1]
The air at 1,800 m is thin and about 10 °C cooler than below. Long soaks in hot sulfur water are tiring up here, so bathe briefly and often. Each inn draws on a different source, so the cloudiness and smell vary a little. Nisshinkan offers 3–6-night 'new toji' plans and morning exercise, a modern version of the therapeutic stays that were Manza's business until the post-war years.[3][2]
The only year-round road is the Manza Highway toll road. From spring to autumn you can also come over from Kusatsu or Shiga Kogen on the Shiga-Kusatsu highland route, but it closes in winter, and volcanic alerts on Mt Kusatsu-Shirane can shut the Sesshogawara–Manza junction stretch at any time. By public transport, Seibu buses take about 40 minutes from Manza-Kazawaguchi Station and about 90 from Karuizawa. Nisshinkan runs guest shuttles from Karuizawa and Naganohara-Kusatsuguchi, booking required.[2][4]
checked 2026-10-09
"Recommended" and "open" are recorded separately. Check the season for seasonal springs.
Dec · Jan · Feb · Mar — Snow bathing and skiing; only the Manza Highway is open, winter tyres essential
Jun · Jul · Aug — About 10 °C cooler than the lowlands; the Shiga-Kusatsu road links to Kusatsu and Shiga Kogen
Oct — Autumn colour in the old-growth forest
Steam vents with hydrogen sulfide; mind the volcanic gas[2]
Edge of the resort, walkableThe slopes run right up behind the hotels; ski, then soak[2]
Adjacent to the resortThe crater lakes above Manza (Yugama, Karekama, Mizugama); access restricted by volcanic activity[2]
About 15 minutes by car on the Shiga-Kusatsu road (spring–autumn)A small pond with a footpath next to the resort[2]
Walk from the resortDecide what you came for: snow bathing in winter, or cool air and the Shiga-Kusatsu road in summer. Bathe briefly on arrival, walk out to the Karabuki vents, then bathe again at dusk. Phone the inns for day-use fees and hours before you go.
The "editors' guide" above is written by the editors from sources; it is not a visitor's opinion.
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.
Updated 2026-10-09
Suggest a correction or addition
