How much do guests actually talk about free-flowing hot spring baths (gensen kakenagashi — spring water fed straight into the tub and allowed to overflow rather than being recirculated)? The HotelBank Editorial Team tallied guest reviews across all 47 prefectures for the most recent 24 months and found 1,254 properties where kakenagashi was mentioned favorably in 10 or more reviews, for a total of 28,913 mentions. The largest mention count nationwide belongs to Fukui Hotel (ふく井ホテル) in Obihiro, Hokkaido, with 274 mentions; the highest mention rates (share of all of a property’s reviews) are at Miyuki Onsen (深雪温泉) in Isawa, Yamanashi (36.0%) and Yamagatakan (山県館) at Kawaura Onsen (30.8%).

For operators, two further points matter. First, the level of estimated settled ADR differs according to what kakenagashi is mentioned together with. Ryokan where it appears in the same review as the open-air bath sit at 1.49x their prefecture’s ryokan benchmark, while ryokan where it is paired only with water quality sit at 0.95x. Second, there are 426 properties where kakenagashi is mentioned in 10 or more reviews yet the mention rate stays below 5%. Most are mid-sized to large properties with many rooms: they have free-flowing baths, but those baths have not become the lead story in their reviews. This article sets out the distribution by prefecture, breaks down how kakenagashi is talked about, examines the relationship with rates, and counts the untapped messaging potential prefecture by prefecture.

Source: HotelBank Editorial Team research (NLP analysis, most recent 24 months) / MetroEngines Research (estimated settled ADR)

Free-Flowing Onsen Ranking — Top 20 Properties by Review Mentions

We start with the national line-up. The table below lists the top 20 properties in descending order of favorable kakenagashi mentions. First-placed Fukui Hotel (Obihiro, Hokkaido) has 274 of its 1,319 reviews touching on kakenagashi, with comments such as “100% free-flowing moor hot spring.” That a business-hotel-style property in front of a station takes first place shows that kakenagashi is not a value reserved for ryokan in hot spring resorts. Second is Yumura Hotel B&B (自家源泉かけ流し天然温泉の宿 湯村ホテルB&B) at Yumura Onsen, Yamanashi (199 mentions), where many reviews go as far as spelling out the water handling: “no heating, no added water, no recirculation…”

The upper ranks also include Yubel Hotel Matsumasa (ユウベルホテル松政) at Yuda Onsen, Yamaguchi (165 mentions), Hotel Oruri (ホテルおおるり) in Shiobara, Tochigi (154), and Bankokuya (萬国屋) at Atsumi Onsen, Yamagata (142) — mid-sized to large properties with a deep base of reviews. Hinoki no Yado Minakami Sanso (檜の宿 水上山荘) in Minakami, Gunma (106 mentions, 18.2%) and Ishizaka Ryokan (石坂旅館) at Ikaho Onsen (102 mentions, 29.3%) score high on both count and rate despite having around 30 rooms or fewer. Because mention counts rise in proportion to total reviews, reading this table alongside the “top mention rate” table below makes it easier to tell the property types apart.

Table 1: Top 20 Properties by Kakenagashi Mention Count (from the population of N=1,254)

Source: HotelBank Editorial Team research (NLP analysis of guest reviews, most recent 24 months, September 2024 – September 2026; properties with 20+ reviews and 10+ positive kakenagashi mentions). Co-mentions are shown as a share of kakenagashi mentions (lower-bound values)

Ranked by mention rate, Miyuki Onsen in Isawa, Yamanashi (36.0%), Guesthouse Yamatoso (ゲストハウス倭荘) in Ito, Shizuoka (32.5%) and Yamagatakan at Kawaura Onsen, Yamanashi (30.8%) come out on top. One review of Yamagatakan describes how “the sight of hot water spilling over the edge of the tub is spectacular,” and roughly one guest in three refers to the way the water is handled. Thirteen of the top 15 have 40 rooms or fewer; these are properties where the water itself is the reason guests choose them.

Table 2: Top 15 Properties by Kakenagashi Mention Rate (properties with 150+ reviews only)

Source: HotelBank Editorial Team research (NLP analysis of guest reviews, most recent 24 months, September 2024 – September 2026; properties with 20+ reviews and 10+ positive kakenagashi mentions). Room counts are from the MetroEngines Research property master

By Prefecture — Shizuoka 135, Nagano 99, Gunma 97; Present in All 47 Prefectures

Counting the 1,254-property population by prefecture, Shizuoka — home to Izu and Atami — has the most at 135, followed by Nagano (99), Gunma (97), Hokkaido (93), Tochigi (81) and Fukushima (75). The top six prefectures account for 46% of the total, yet urban prefectures such as Tokyo, Osaka, Kyoto and Aichi each have a few qualifying properties as well: every one of the 47 prefectures has properties where kakenagashi is talked about.

The bar colors show the four mention-pattern types explained below. In most of the leading prefectures the “Water quality + open-air” type is the largest block, but the “Water-quality paired” type exceeds 30% in Kanagawa, Yamagata and Fukushima, and the “Open-air paired” type exceeds 20% in Shizuoka and Oita. Even for the same kakenagashi, hot spring areas divide into those talked about for the character of their water and those talked about together with open-air baths and sea views.

Source: HotelBank Editorial Team research (NLP analysis of guest reviews, most recent 24 months, September 2024 – September 2026; properties with 20+ reviews and 10+ positive kakenagashi mentions). Top 25 prefectures

Table 3: Population by Prefecture (47 prefectures, N=1,254)

Source: HotelBank Editorial Team research (NLP analysis of guest reviews, most recent 24 months, September 2024 – September 2026; properties with 20+ reviews and 10+ positive kakenagashi mentions). Property names are omitted for prefectures with two or fewer qualifying properties

Is Kakenagashi Mentioned on Its Own? — 21.1% Share a Review with Water Quality, 17.3% with Open-Air Baths

Next, we break down the context in which kakenagashi is mentioned. Of the 28,913 kakenagashi mentions in the population, 21.1% also referred favorably to water quality (skin-beautifying water, milky or cloudy water, a silky texture and so on) in the same review, and 17.3% also referred to the open-air bath. By contrast, only 1.2% were mentioned together with bath-hopping (yumeguri, the experience of touring several baths). Guests write about kakenagashi in connection with “the quality of the water” and “the experience in the open-air bath,” and much less in connection with the number of different baths. The properties rated for water quality itself are analyzed in detail in Chosen for the Water: Japan’s Top 30 Onsen Inns by Review Mentions.

Source: HotelBank Editorial Team research (NLP analysis of guest reviews, most recent 24 months, September 2024 – September 2026; properties with 20+ reviews and 10+ positive kakenagashi mentions). N = 28,913 kakenagashi mentions. Co-mention figures are lower bounds, because up to three co-mentions per property may be missed for lower-ranked properties in the prefecture-level tabulation

At the property level, the four types — defined by a co-mention rate of 10% or more — break down into 568 “Water quality + open-air,” 331 “Water-quality paired,” 180 “Standalone” and 175 “Open-air paired” properties. Properties where kakenagashi is talked about on its own make up just 14% of the total; at most properties it is remembered together with either the quality of the water or the scenery of the bath. The way reviews are written is also distinctive. Minakami Sanso draws comments such as “no added water, no heating and no chlorine disinfection,” and Yumura Hotel B&B “no heating, no added water, no recirculation…” — guests are putting into their own words the water-handling information the property has posted and explained.

Japan’s Hot Springs Act requires bathing facilities to post whether water is added, heated, recirculated and filtered, or treated with bath additives or disinfectant, together with the reasons (Article 18 of the Hot Springs Act; Article 10 of its Enforcement Regulations). The scope of these notices differs by property — “all tubs,” “open-air bath only,” “private baths only” — so properties that spell out, on their official website and on site, which tub uses which kind of water handling are likely the ones whose guests find it easiest to put into words.

Relationship with Rates — Ryokan in the Population at 1.23x the Prefectural Benchmark, Open-Air Paired Type at 1.49x

From here we look at the relationship with estimated settled ADR. Narrowing to the ryokan category to hold property type constant, there are 958 ryokan in the population with an estimated settled ADR, with a median of ¥17,600. Compared with the ryokan benchmark of the prefecture where each is located, the median ratio is 1.23x, and the population exceeded the prefectural benchmark in 23 of the 26 prefectures that have eight or more qualifying ryokan. Ryokan where kakenagashi is talked about generally sit in the upper price band among ryokan in their prefecture.

However, a higher mention rate does not mean a higher rate. Splitting the ryokan into thirds by mention rate, the bottom third (0.4–5.2%) is at 1.45x the prefectural benchmark, the middle third at 1.27x and the top third (10.9% and above) at 0.96x — the order is, if anything, reversed. Median room counts are 42 for the bottom third and 13.5 for the top third: the high-mention-rate group consists mainly of small properties that make the water itself their signature, while the low group consists mainly of mid-sized to large properties with many other things to talk about, such as cuisine, views and in-house facilities. Mention rate is best read as a yardstick of “how far the water is the star of the property,” which is a different thing from a yardstick of rates.

Where the difference in rates shows up clearly is in the mention-pattern type. Ryokan of the “Open-air paired” type, where kakenagashi is mentioned together with the open-air bath, are at 1.49x the prefectural benchmark (N=129); the “Water quality + open-air” type is at 1.30x (N=462), the “Standalone” type at 1.22x (N=117) and the “Water-quality paired” type at 0.95x (N=250). The Water-quality paired type has a median of 17 rooms and a median mention rate of 11.1%, and includes many small inns with a tradition of toji (therapeutic bathing stays). Properties where kakenagashi is paired with the open-air bath are selling it as “time spent within the scenery,” and that experience is likely easier to reflect in the rate. How open-air bath views are rated in reviews is explored region by region in Review NLP Maps Japan’s Top Scenic Open-Air Bath Regions.

Source: MetroEngines Research (estimated settled ADR, September 2025 – August 2026) / HotelBank Editorial Team research (NLP analysis). 958 ryokan-category properties with an estimated settled ADR. Prefectural ryokan benchmark = monthly average of estimated settled ADR for ryokan by prefecture over the same period

Table 4: Estimated Settled ADR by Mention Pattern and Mention Rate (ryokan, N=958)

Source: MetroEngines Research (estimated settled ADR, September 2025 – August 2026) / HotelBank Editorial Team research (NLP analysis)

This comparison is a descriptive association; it does not show how much kakenagashi or an open-air bath in itself lifts the rate. Location, room size, cuisine and whether rooms have private open-air baths are all at work at the same time. Isolating the premium of a single facility requires a different method — comparing room types within the same property — which is outside the scope of this article.

Prefectures Where Kakenagashi Is Rare — Under 0.1% of Local Reviews, and a Differentiator for Properties That Earn It

At the prefecture-wide level, there are regions where mentions of kakenagashi are extremely scarce. Kakenagashi mentions as a share of all reviews in the prefecture come to 0.010% in Osaka, 0.012% in Tokyo, 0.029% in Okinawa, 0.054% in Kyoto, 0.065% in Aichi, 0.072% in Hiroshima and 0.090% in Kochi — all below 0.1%. In these regions most accommodation demand is urban sightseeing or business travel, and because hot spring options are themselves few, a property where kakenagashi is talked about stands out within its prefecture.

Table 5: Prefectures Where Kakenagashi Mentions Are Rare, and Examples of Properties Mentioned

Source: HotelBank Editorial Team research (NLP analysis, most recent 24 months). Mention share is the share of all reviews in the prefecture. Osaka (0.010%, one qualifying property) is omitted from the table

For properties in metropolitan areas, kakenagashi works not as “a weapon for competing on the same ground as inns in hot spring resorts” but as “a feature with no substitute inside the prefecture.” In cases such as the black-water (kuroyu) hot spring in Kamata, it is mentioned together with proximity to the station, making it a feature that can appeal to both business and leisure demand.

Untapped Messaging Potential — 426 Properties Have Kakenagashi but a Mention Rate Below 5%

Finally, the main point for operators. Every property in the population has 10 or more reviews speaking favorably of kakenagashi — in other words, guests have actually experienced and rated its free-flowing baths. Of these, 426 properties (34% of the total) have a mention rate below 5%, and together they account for 336,445 reviews, or 63% of all reviews in the population. Their median mention rate is 2.9%, which works out to only about one guest in 35 referring to kakenagashi.

These 426 properties have a median of 49 rooms, about three times the size of properties with a mention rate of 5% or more (16 rooms), and their ryokan sit in a high price band, with estimated settled ADR at 1.46x the prefectural benchmark (median ¥20,600, N=310). By room count, properties with 10 rooms or fewer have a median mention rate of 14.5% and only 8.6% fall below 5%, whereas for properties with 81 rooms or more the median mention rate is 2.1% and 83.8% fall in the below-5% band. The larger the property, the more there is to talk about — cuisine, views, in-house facilities — and the pattern suggests that free-flowing baths are relatively easily buried within the reviews.

Source: HotelBank Editorial Team research (NLP analysis of guest reviews, most recent 24 months, September 2024 – September 2026; properties with 20+ reviews and 10+ positive kakenagashi mentions). 1,253 properties with a known room count

By prefecture, properties with a mention rate below 5% are most numerous in Shizuoka (44), Hokkaido (43), Gunma (41), Nagano (28), Oita (25), Yamagata and Kanagawa (21 each) and Tochigi (19), in that order. In Hokkaido, Gunma and Oita, 40–50% of the population falls into this band; the more a hot spring area is home to large onsen ryokan and resort hotels, the greater the untapped potential.

Source: HotelBank Editorial Team research (NLP analysis of guest reviews, most recent 24 months, September 2024 – September 2026; properties with 20+ reviews and 10+ positive kakenagashi mentions). Top 15 prefectures by number of properties with a mention rate below 5%

The moves for capturing this potential can be grouped into three. First, state the water handling specifically, tub by tub. At large properties it is common for only part of the main bath to be free-flowing; describing “which tubs are free-flowing from the source, and whether water is added or heated” separately on the bath page of the official website and in plan descriptions makes it easier for guests to put it into words. Second, present it together with the open-air bath and the water quality. As the previous section showed, properties where kakenagashi is paired with the open-air bath have higher rate levels, and positioning kakenagashi as “time with the scenery and the water” fits well with sustaining rates. Third, offer stay plans built around the baths. Check-in and check-out times that leave a long stretch after bathing, and clear guidance on baths that are open through the night, are things guests do pick up on in reviews, with phrases such as “free-flowing baths you can use 24 hours a day” and “all through the night…”

Note that a low mention rate does not mean the water is poorly rated. Of the kakenagashi mentions in the population, 99.5% were in a favorable context (1,120 properties and 26,657 mentions for which a breakdown was available). When guests do mention kakenagashi, they speak of it favorably almost without exception. There is room for more frequent mentions to translate directly into a deeper base of positive ratings for the property.

On the Map — Distribution of the 1,253 Properties Where Kakenagashi Is Talked About

Plotting the population on a map, dense bands appear on the Izu Peninsula, in Hakone, in northern Gunma (Kusatsu, Ikaho and Shima), in Nasu and Shiobara, in Shinshu (Nagano), along the Ou Mountains in Tohoku, in Beppu and Yufuin, and in southern Kyushu. Dot color shows the mention-pattern type and size shows the mention rate (property names are shown only for properties with a mention rate of 5% or more; names appear in Japanese).

Source: HotelBank Editorial Team research (NLP analysis, most recent 24 months), MetroEngines Research

Summary

There are 1,254 properties nationwide where free-flowing hot spring baths are mentioned in 10 or more guest reviews, spread across all 47 prefectures. Kakenagashi is often mentioned in the same review as water quality (21.1%) and open-air baths (17.3%), and ryokan where it is paired with the open-air bath have an estimated settled ADR of 1.49x their prefecture’s ryokan benchmark. The mention rate itself is higher at small, toji-style inns and runs in the opposite order to rates, so it is best read as “the degree to which the water is the star of the property.”

The untapped potential for operators lies in the 426 properties that have free-flowing baths and are rated for them by guests, yet where the share of reviews mentioning them stays below 5%. Most are mid-sized to large properties with many rooms, priced above their prefecture’s ryokan benchmark. Disclosing water handling tub by tub, presenting kakenagashi together with the open-air bath and water quality, and designing plans around the baths are three moves that can be taken with existing facilities.

Frequently Asked Questions

Q. How many properties nationwide have free-flowing hot spring baths that guests mention in reviews?

There are 1,254 properties across the 47 prefectures with 20 or more reviews in the most recent 24 months (September 2024 – September 2026) and 10 or more favorable mentions of kakenagashi, for a total of 28,913 mentions. By prefecture, Shizuoka (135), Nagano (99), Gunma (97) and Hokkaido (93) have the most, and urban prefectures such as Tokyo, Osaka, Kyoto and Aichi each have a few qualifying properties.

Q. Should I look at mention count or mention rate?

It depends on the purpose. Mention count rises in proportion to total reviews, so it is a metric on which mid-sized to large properties with many reviews tend to rank high. Mention rate is the share of all reviews that touch on kakenagashi; the population median is 7.7% (interquartile range 3.9–13.7%). The top of the mention-rate ranking consists mainly of small properties with 40 rooms or fewer, which makes it suited to finding properties where the water itself is the reason guests choose them.

Q. Do ryokan where kakenagashi is talked about command higher rates?

The 958 ryokan in the population with an estimated settled ADR were at a median of 1.23x the ryokan benchmark of their prefecture. However, a higher mention rate does not mean a higher rate: the top third by mention rate is at 0.96x. The clear difference lies in how kakenagashi is talked about — the Open-air paired type, mentioned together with the open-air bath, was at 1.49x (N=129), while the Water-quality paired type, mentioned only with water quality, was at 0.95x (N=250). This is a descriptive association and does not show how much kakenagashi or an open-air bath in itself lifts the rate.

Q. What kind of properties are the 426 with “untapped messaging potential”?

They are properties with 10 or more reviews speaking favorably of kakenagashi but a mention rate below 5%. They are mainly mid-sized to large, with a median of 49 rooms, and their ryokan have an estimated settled ADR of 1.46x the prefectural benchmark (N=310). Among properties with 81 rooms or more, 83.8% fall into this band. By prefecture, Shizuoka (44), Hokkaido (43) and Gunma (41) have the most.

Q. Where should a property start if it wants kakenagashi to be mentioned in reviews?

There are three moves that can be taken with existing facilities: state the water handling tub by tub (whether water is added, heated, or recirculated and filtered) on the bath page of the official website and in plan descriptions; present kakenagashi together with the open-air bath and the water quality; and offer stay plans built around the baths. The Hot Springs Act requires water handling to be posted at the bath (Article 18; Article 10 of its Enforcement Regulations), and surfacing that information at pre-booking touchpoints as well makes it easier for guests to put into words.

Methodology and Sources

• Guest reviews use data for the most recent 24 months (September 2024 – September 2026) that the HotelBank Editorial Team has classified into 79 evaluation items through natural language analysis. Favorable mentions of free-flowing hot spring baths were tallied prefecture by prefecture, and properties with 20 or more reviews and 10 or more mentions form the population (1,254 properties).
• Co-mentions count, for each property, the reviews that refer favorably to both kakenagashi and water quality, the open-air bath or bath-hopping within the same review, divided by the number of kakenagashi mentions. Because up to three co-mentions may be missed for lower-ranked properties in the prefecture-level tabulation, the figures are treated as lower bounds.
• Estimated settled ADR is the monthly average for properties with estimates for six or more months between September 2025 and August 2026 (1,117 properties, of which 958 are ryokan). The prefectural ryokan benchmark is the monthly average of estimated settled ADR for the ryokan category by prefecture over the same period.
• Kakenagashi mentions as a share of reviews in the prefecture are measured against all reviews in the prefecture (including properties with few reviews), and are reported for prefectures where kakenagashi appeared in a tabulation of evaluation items ordered from the rarest.
• Review quotations are partial quotations, and reviewer attributes are not used.

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