What the Hoshi Onsen Chojukan Large Bath Is
The Hoshi Onsen Chojukan Large Bath (Hoshi-no-Yu) (法師温泉長寿館大浴場（法師乃湯）, Hōshi Onsen Chōjukan Daiyokujō, Hōshi-no-Yu) is a single-story timber bathhouse built in 1895 on the east bank of the Hoshi River, just north of the inn's Main Building, in Nagai, Minakami Town, Gunma Prefecture, and was registered as a Registered Tangible Cultural Property on August 3, 2006.
Hoshi-no-Yu is the oldest of the inn's baths. The building measures 12 meters by 10 meters, with a footprint of 119 square meters. Its hipped roof, in the Yosemune-zukuri form, is covered in cedar bark, and the outer walls are clad in overlapping horizontal boards, a technique known as Shitami-itabari.
What sets it apart as a bathhouse is that the water rises through the bottom of the pool. The inn explains that a timber frame was built on the riverbed and the space inside it became the bath, so spring water welling up from the bedrock fills the pool directly. It is, the inn says, almost never heated, diluted or recirculated.
Why Hoshi-no-Yu Was Registered
The Hoshi Onsen Chojukan Large Bath was registered under the criterion of contributing to the historic landscape of the country, as registration number 10-0189.
The Agency for Cultural Affairs singles out its arched windows as the building's distinguishing design feature. Round-topped Western-style openings set into a cedar-bark and clapboard mountain building are the heart of the assessment. The inn calls the windows Rokumeikan style, after the Western-style reception hall built in Tokyo in the 1880s, and lists them among the points recognized at registration.
What to Look For in Hoshi-no-Yu
The Arched Windows
A row of openings with rounded heads runs along the clapboard walls of Hoshi-no-Yu. On bright days, the inn notes, light through the arches catches the steam and makes it stand in the air like columns. The shape reads best looking up from the water.
An Open Roof Structure
There is no ceiling over the bath, so the roof framing is fully exposed. According to the Agency's description, the structure is basically a Wagoya, the Japanese system of posts and heavy beams, with Western-style trusses used in part. That mix of a traditional frame with triangulated Western members fits its date of 1895.
On the ridge sits a ventilator shaped like a small watchtower, built to draw steam out through the roof. From outside it reads as a second, smaller roof perched on the peak of the hipped roof. The eaves on all four sides project deeply in the segai-zukuri manner.
Pools Divided by Logs
Thick logs split the bath into four pools, and bathers rest their heads on them. Look down into the water and you can see the spring rising from the bottom in a stream of bubbles.
Visiting Hoshi-no-Yu
The only way to see inside the Hoshi Onsen Chojukan Large Bath is to bathe in it. It is open both to overnight guests and to day visitors.
Hoshi-no-Yu is mixed-gender, and bathing garments or towels wrapped around the body are not allowed. For overnight guests, 8:00 p.m. to 10:00 p.m. is reserved for women. The bath closes 10:00 a.m. to 11:00 a.m. for cleaning.
The inn's website sets out no rule on photography in the baths. Do not point a camera at a bath where others are bathing, and ask the inn beforehand if you want pictures. The exterior, with its rooftop ventilator and row of arched windows, can be seen from the north side of the Main Building. Day-bathing hours, fees and travel directions are on the Hoshi Onsen Chojukan page.
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Q&A
- When was the Hoshi Onsen Chojukan Large Bath (Hoshi-no-Yu) built?
- In 1895. It was registered as a Registered Tangible Cultural Property on August 3, 2006.
- Can day visitors bathe in Hoshi-no-Yu?
- Yes. Day bathing runs 11:00 a.m. to 2:00 p.m. (reception until 1:30 p.m.) and is unavailable on Wednesdays, according to the inn's website as of September 25, 2026.
- Is Hoshi-no-Yu mixed bathing, and can I wear a bathing garment?
- It is mixed-gender, and bathing garments or wrapped towels are not permitted. Overnight guests can use the women-only hours of 8:00 p.m. to 10:00 p.m.
- Why does Hoshi-no-Yu have arched windows?
- No record of the builders' intent has been found. The windows reflect Western design ideas of the Meiji era, and the Agency for Cultural Affairs names them as the building's distinctive design feature.
- Where does the water in Hoshi-no-Yu come from?
- It wells up directly from the bedrock beneath the pool. The inn describes it as a spring that rises underfoot and is almost never heated, diluted or recirculated.
Basic Information
| Name | Hoshi Onsen Chojukan Large Bath (Hoshi-no-Yu) |
|---|---|
| Location | 650 Nagai, Minakami-machi, Tone-gun, Gunma Prefecture, and others |
| Designation | Registered Tangible Cultural Property (Building) |
| Year Designated | Registered August 3, 2006 |
| Quantity | 1 building |
| Dimensions | 12 meters by 10 meters; footprint 119 square meters |
| Owner | Hoshi Onsen Chojukan Co., Ltd. |
| Public Access | Operating bath. Open to overnight guests and day bathers |
References
- Agency for Cultural Affairs, Database of National Cultural Properties: Hoshi Onsen Chojukan Large Bath (Hoshi-no-Yu)
- https://kunishitei.bunka.go.jp/bsys/maindetails/101/00005583
- Cultural Heritage Online: Hoshi Onsen Chojukan Large Bath (Hoshi-no-Yu)
- https://online.bunka.go.jp/heritages/detail/142851
- Hoshi Onsen Chojukan official website: Onsen
- https://hoshi-onsen.com/onsen/
- Hoshi Onsen Chojukan official website
- https://hoshi-onsen.com/
- Japan Association to Protect Secluded Hot Springs: Hoshi Onsen Chojukan
- https://www.hitou.or.jp/provider/detail?providerId=626
Last verified: 2026.09.25
