Wild spring · Seasonal
Sennin-buro
- Day-use bathing
- Yes
- Fee
- ¥0checked 2026-10-09
- Hours
- 6:30–22:00checked 2026-10-09
Photo information
Save to passport
Official classification
Spring type (therapeutic classes)
Official spring-type name (as recorded)Sodium bicarbonate and chloride spring
- Source temperature
- 73°C
- pH
- Unconfirmed
- Flow rate
- Unconfirmed
- Radon
- Unconfirmed
Appearance & feel
Water colour · Feel
Clear
Colour and feel are listed only where a source states them. They vary by day and by bath.
What makes it special
Dig into the riverbed and hot water wells up. In winter they dam the river itself and turn it into an open-air bath for a thousand.
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.
Public bathhouse · Open
Kawayu public bathhouse
- Day-use bathing
- Yes
- Fee
- ¥300checked 2026-10-09
- Hours
- 6:30–20:00checked 2026-10-09
Ryokan (inn) · Open
Sansuikan Kawayu Matsuya
- Day-use bathing
- Unconfirmed
- Fee
- Unconfirmedno check date
- Hours
- Unconfirmedchecked 2026-10-09
Getting there
Reachable by public transport
From JR Kii-Tanabe Station take the Ryujin Bus Kumano Hongu line to 'Kawayu Onsen' (about 2 hours). From JR Shingu Station it is about an hour by bus. Local buses link Hongu Taisha and Yunomine.
- Getting there
- Kii-Tanabe Station · 120
- Getting there
- A handful a day; see the Ryujin Bus timetable
- Through the year
- Sennin-buro runs Dec–Feb only; the river is off-limits when high
- Checked
- 2026-10-09
About the water
Water at 73°C rises through the gravel of the riverbed: an alkaline bicarbonate-chloride spring, clear and mild. What makes Kawayu interesting is not its chemistry but how it emerges. Dig and the hole fills with hot water, which you blend with the cold river to taste. In winter the river runs low enough to be dammed and turned into a single great tub, the Sennin-buro, kept near 40°C by letting river water into the hot seep. Indications were not readable and are omitted.
| Source | Source temperature | pH | Radon | Checked |
|---|---|---|---|---|
| Kawayu | 73 | Unconfirmed | Unconfirmed | no check date |
Three things not to miss
Photo information
Sennin-buro
On the Oto River From December to the end of February the river is dammed into a huge open-air pool. 6:30–22:00, free, swimsuits compulsory. River water is let in to hold it around 40°C.
Its size changes year to year. On Saturday nights lanterns are lit along the riverbed.[2]
Photo information
Dig your own bath
Oto riverbed (outside the Sennin-buro season) Dig the gravel with a shovel, mix the hot seep with river water and make your own tub. Non-guests bring their own tools.
You can prove to yourself that 73°C water is rising through the riverbed.[1][7]
The public bathhouse
In the village A communal bath at 300 yen. 6:30–20:00, closed Tuesdays; soap and towels cost extra.
The one cheap place with a roof to wash after playing in the river.[3]
The story
Up through the riverbed
Kawayu's water rises through the bed of the Oto River: a 73°C sodium bicarbonate-chloride spring. Dig into the gravel and the hole fills with hot water; blend in cold river water and you have your own open-air bath. Few places let you confirm so directly that there is hot water under the ground.[1][7]
The bath of a thousand
When the river drops in winter, the flow is dammed and the whole river becomes a bath. This is the Sennin-buro, a custom said to date from the early Edo period. It runs from December to the end of February, 6:30 to 22:00, free, in swimsuits; its size changes every year. On Saturday nights lanterns line the riverbed.[2][7]
Three springs of Hongu
Kawayu, with Yunomine and Watarase, was designated a National Recreation Hot Spring in 1957, and eleven lodgings line its river. Hongu Taisha is about 15 minutes away by bus, Yunomine's Tsuboyu about 10, making it a base for walking the Kumano Kodo. Buses come in from both Kii-Tanabe and Shingu, but not many.[1][7]
Going solo
Easy for solo travellersYes
Weekend / peak restrictionsUnconfirmed
Where to eat dinnerFew eateries; dine at your inn
Private bathUnconfirmed
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.
Dec · Jan · Feb — Sennin-buro season; lantern nights on Saturdays
Apr · May · Oct · Nov — Season for digging your own bath; combine with Kumano Kodo walking
Jul · Aug — River play and hot water; beware of high water
Food, culture & experiences
Kumano Hongu Taisha
One of the three Kumano grand shrines[1]
10–15 min by busYunomine Onsen Tsuboyu
World Heritage rock bath[1]
About 10 min by busYukemuri lantern nights
During the Sennin-buro season, Saturdays about 20:00–22:00[2]
At the Sennin-buroDigging a riverbed bath
Bring a shovel; some inns lend them to guests[1]
Oto RiverEditors' guide
In winter bring a swimsuit for the Sennin-buro. In spring or autumn borrow a shovel from your inn, dig the riverbed and set your own temperature. Soap is not allowed in the river, so finish at the public bathhouse. Yunomine's Tsuboyu can be done the same day.
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.
Onsen areas nearby
Unconfirmed & notes
- Source pH, mineral content and indications not confirmed
- The bathhouse page reads 'alkaline simple spring' while the association's onsen page and the ledger say bicarbonate-chloride; unresolved
- Bus frequency and times need checking against current timetables
Sources
- 熊野本宮観光協会 川湯温泉熊野本宮観光協会 · 2026-10-09
- 仙人風呂熊野本宮観光協会 · 2026-10-09
- 川湯温泉公衆浴場熊野本宮観光協会 · 2026-10-09
- 川湯温泉の宿熊野本宮観光協会 · 2026-10-09
- 交通案内(道路状況・バス)熊野本宮観光協会 · 2026-10-09
- 龍神バス 熊野本宮線龍神自動車 · 2026-10-09
- 川湯温泉 (和歌山県) - WikipediaWikipedia · 2026-10-09
Register sources
- 川湯温泉 (和歌山県) - Wikipedia(日本語版)Wikipedia · CC BY-SA 4.0 · 2026-10-09
- Wikidata Q11478936Wikidata · CC0 · 2026-10-09
Data status
Name & locationPublishedCoordinatesPublishedSpring typePublishedPhotosPublishedFacilitiesPublishedVisiting info (dated)PublishedEditorial articlePublished
Updated 2026-10-09
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