Right Onsen › Gunma › Minakami
Mantenboshi no Yu.
4.0★ · 1450 Google ratings · Minakami, Gunma · まんてん星の湯
✓ Private day-use bath✓ Natural hot-spring water✓ Free-flowing source water✓ Outdoor bath✓ Rest area✓ Restaurant
Before you go
Can you bathe here?
Tattoos
Not allowedstated on the facility's website · read 2026-09
Hours
10:00–20:00 · closed Tuesdayfrom the facility listing
Price
¥950The standard 3-hour outside-town admission is 950 yen, with an 1800 yen full-day option; visitors note the price has risen recently.stated by 3 visitors · Jun 2026 – Jul 2026
Time limit
Tiered: 3h / 5h / 1-dayAdmission is sold in time tiers (3 hours, 5 hours, or full day) at increasing prices.stated by 2 visitors · Feb 2026 – Jul 2026
Watch out
Restaurant
An on-site restaurant (kazaguruma) is well regarded by some, but multiple reviewers report waits of around two hours for food and overcooked/poor-quality dishes.
stated by 6 visitors · Feb 2026 – Jul 2026The bath
What you’ll find
A large, well-appointed lake-view day-spa in Sarugakyo with a hot 58C source, two named outdoor baths, a distinctive low-temperature 'bona sauna' and cold bath, undercut by a paid hair-dryer system and repeated complaints of two-hour restaurant waits.
Outdoor bath
✓ YesExtensive outdoor bathing area overlooking the reservoir, widely praised.stated by 10 visitors · Feb 2026 – Aug 2026
Sauna
✓ YesHas a distinctive low-temperature (~86C) 'bona sauna' with a view, well liked by sauna enthusiasts.stated by 6 visitors · Feb 2026 – Jul 2026
Cold bath
✓ YesA cold plunge bath is available; its temperature varies noticeably by season, from over 20C in summer to under 15C in winter.stated by 4 visitors · Jun 2026 – Aug 2026
View
RiverThe outdoor baths overlook a dam reservoir (Akadani-ko); most reviewers rate the view highly, though one felt it was overstated and not really on a hilltop.stated by 3 visitors · Feb 2026 – Aug 2026
Rest area
✓ YesSpacious tatami rest areas and reservable private rest rooms are available, though one reviewer found the general rest corner more simple (chairs and a rug rather than tatami).stated by 4 visitors · Feb 2026 – Jul 2026
Restaurant
✓ YesAn on-site restaurant (kazaguruma) is well regarded by some, but multiple reviewers report waits of around two hours for food and overcooked/poor-quality dishes.stated by 6 visitors · Feb 2026 – Jul 2026
The water
Free-flowing (kakenagashi)
PartlyOne indoor bath is genuinely source-fed (kakenagashi) while a second indoor bath mixes source water with filtration; the very hot source is also diluted/flow-reduced to bring temperatures down.stated by 4 visitors · Feb 2026 – Aug 2026
Spring type
Calcium-sodium sulfateClassified as a calcium-sodium sulfate spring, giving a soft, skin-friendly feel.stated by 1 visitor · May 2026
Source temperature
58°CSpring source temperature is 58C.stated by 2 visitors · Jun 2026 – Aug 2026
Bath temperature
43°CThe main hot bath runs around 43C, which some visitors find too hot to comfortably soak in.stated by 2 visitors · Jun 2026 – Jul 2026
Practical
What to bring
Hair dryer
PaidHair dryers cost 100 yen per 5 minutes; a frequently repeated complaint though the units are good quality (Dyson).stated by 7 visitors · Feb 2026 – Jul 2026
Guide
What visitors add
The water
One reviewer identifies the water as a calcium-sodium sulfate spring; the source is 58°C (two reviewers). Character is clean and mild: colorless/odorless with no slippery texture but strongly warming (one), 'no quirks' (one), soft (one), and slow to let you chill afterwards (one); one reviewer caught a faint sulfur smell in 2023.
stated by 7 visitors · Feb 2026 – Aug 2026Outdoor bath & sauna
The open-air baths overlooking Akaya Lake are the facility's star feature — at least six reviewers praise the view; one details two outdoor areas ('Sato no Yu' stone garden and 'Tanabata no Yu'), another that the rotenburo is partitioned so families/groups can soak separately, and others mention shallow/deep/hot/lukewarm sections, a lying bath (neyu), a seasonal apple bath, and outdoor washing stations.
stated by 7 visitors · Feb 2026 – Aug 2026Price
Admission is time-tiered (3-hour, 5-hour, and 1-day tickets — two reviewers describe the system): non-town-resident 3 hours costs 950 yen (three reviewers in 2026) and a full day 1800 yen (one reviewer). Two reviewers note prices were recently raised.
stated by 6 visitors · Feb 2026 – Jul 2026Outdoor bath & sauna
There is a 'Bona' sauna with a window view — a rarity fans travel for (one regular visits repeatedly for it): mild rather than punishing, around 86°C per one reviewer, 'not a crazy-hot sauna' per another. The cold bath swings with the seasons: warm (20°C+) in summer per two reviewers, but below a felt 15°C in winter per one.
stated by 6 visitors · Feb 2026 – Aug 2026Towels, soap & lockers
Hair dryers cost 100 yen per 5 minutes — six reviewers flag this (they are premium Dyson-class units; one says the charge began around 2025 and advises bringing your own).
stated by 6 visitors · Feb 2026 – Jul 2026The water
Bath temperature is a recurring complaint in summer 2026: two reviewers estimate about 43°C or more ('hard to soak to the shoulders'), and reviewers conflict on the lukewarm tub — one found the nuru-yu 'too cold', another says even the nuru-yu was 'normally hot'; winter visitors instead call the outdoor bath pleasantly warm (two reviewers).
stated by 5 visitors · Feb 2026 – Jul 2026Timing
When to go
Quietest Wednesday around 10:00; busiest Saturday around 17:00. Measured by Google over past visits, not a forecast.
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Quiet Busy
| Day | Hours |
|---|---|
| Monday | 10:00–20:00 |
| Tuesday | Closed |
| Wednesday | 10:00–20:00 |
| Thursday | 10:00–20:00 |
| Friday | 10:00–20:00 |
| Saturday | 10:00–21:00 |
| Sunday | 10:00–21:00 |
Closed Tuesday.
Practical
Plan your visit
📍 1150-1 Sarugakyoonsen, Minakami, Tone District, Gunma 379-1403
🚃 Kamimoku station, 8.4 km
📞 +81278-66-1126
📋 Show at the counter: まんてん星の湯
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