Sauna is a Finnish word, but the practice of warming the body with steam has old roots in Japan as well. From a single bathhouse in Ginza to the Olympic village, the back-street buildings of the Showa era and the super sento of the suburbs, this is the path sauna has taken in Japan, traced alongside the country's own memory of steam.
The origin of Japanese bathing culture lies not in soaking in hot water but in bathing in steam. In western Japan especially, various forms of steam bathing were practised long before the Edo period.
Along the western coast of the Seto Inland Sea, in Yamaguchi and Oita, many remains of the ishiburo, or stone bath, survive: sealed chambers cut into caves and rock walls where dried leaves were burned so that bathers could sweat in the heat and steam. In Yase, Kyoto, the dome-shaped kamaburo has been handed down, together with the legend that Prince Oama, later Emperor Tenmu, recuperated here from wounds suffered in the Jinshin War. A legend it remains, but it speaks to how old the bond between steam and healing is.
The arrival of Buddhism made steam bathing a rite of purification. Temples built bathing halls, and from the Kamakura through the Muromachi periods the custom of seyoku, opening those halls to the sick and the poor, flourished, as picture scrolls attest. Kennin-ji, founded in 1202, had a bathing room where monks sat in zazen amid the steam for the time it took a stick of incense to burn down, roughly thirty minutes. Time spent quietly facing oneself in the heat: the sensation today's sauna lovers know so well may already have existed in the bathhouse of a Zen temple.
The sento of Edo were steam baths of a kind as well. In the todanaburo, bathers soaked their lower body in knee-deep water while sliding doors trapped the steam that warmed their upper half. Japan's relationship with steam, in other words, had been going on long before the Finnish word ever arrived.
The stage for the word's arrival in Japan was Ginza. In 1951, a leisure bath complex called Tokyo Onsen opened in Ginza 6-chome, complete with steam baths, private rooms, massage rooms and even a cabaret. A private bath cost 600 yen at a time when the neighbourhood sento charged 12. It was an extravagantly luxurious bathhouse.
Its founder, Ujitoshi Konomi, was a businessman from Fukuoka and a competitive clay pigeon shooter. Competing for Japan at the 1956 Melbourne Olympics, he encountered the saunas used by Finnish and other foreign athletes in the Olympic village. On his return he built a sauna bath at Tokyo Onsen. Sources date the installation to either 1956 or 1957; it seems to have happened around the end of 1956 or in 1957, after his return from Melbourne. In the lineage traced by the Japan Sauna and Spa Association, this is where the country's sauna industry begins.
Where to place Japan's first sauna, though, depends on the definition. The sauna at Tokyo Onsen was a Japanese adaptation that used steam piping as its heat source, and differed, so the argument goes, from a Finnish stove sauna. The first authentic Finnish sauna in Japan comes a little later in the story.
At the 1964 Tokyo Olympics, a full-scale sauna was built in the Yoyogi Olympic village. It is said to have been installed at the request of the Finnish and other athletes, and some regard it as Japan's first authentic Finnish-style sauna.
Media coverage of the village sauna made the word known across the country almost overnight. After the Games, saunas spread to sports facilities and sento, and the first sauna boom arrived. Finnish steam had flowed into Japanese daily life by way of a festival of sport.
During the years of high economic growth, sauna put down roots in the districts where men worked. As a place to recover quickly between long working hours, the high-temperature dry sauna of around 100 degrees, the so-called Showa Strong style, became the norm. By 1971 there were said to be 440 saunas in Tokyo alone.
Most dedicated sauna facilities outside the sento were men-only, and they soon became entwined with the capsule hotel. Capsule Inn Osaka, the first of its kind, opened in Umeda, Osaka in 1979; the sauna operator New Japan Kanko commissioned the architect Kisho Kurokawa to design it. Sweat in the sauna, sleep in a capsule. The image of the sauna as a place for middle-aged men took shape in this era.
The 1973 oil crisis struck the industry through soaring fuel costs, and the roughly 4,000 facilities nationwide are said to have fallen by half. Still, the steam never went out. The 1980s brought the kenko land, which combined large baths and saunas with theatre, karaoke and dining, and became the doorway through which women and families first met the sauna.
In 1989, Ryusenji no Yu opened in Moriyama, Nagoya. Born of the idea of offering more than a kenko land at neighbourhood sento prices, it is considered the first super sento. The idea belonged to its founder, Shoichi Matsunaga, who had been in the sauna business since 1960. Openings followed across the country from the late 1990s into the early 2000s; by one count, some 770 facilities existed by 2009.
With sauna included in the price of admission, the sauna changed from a men-only special place into an everyday one for families. It was this widened base that let the next boom reach so deep and so wide.
The starting point of the third boom, which continues today, was a book. Sado, an essay by the manga artist Katsuki Tanaka, appeared in book form in 2011 and as a manga in 2016. In 2019 it became a television drama starring Taizo Harada, and sauna reached a general audience all at once.
The word that defines this boom is totonou, roughly, to come into balance: the deep state of calm that follows the cycle of sauna, cold plunge and open air. The term is said to have been coined by the pro sauna bather known as Nurezukin-chan and spread by Tanaka through Sado. Sauna Ikitai, a search site launched by four volunteers in 2017, passed 15,000 listed facilities in 2025.
There is a side to this boom that amounts to a return to Finland. Where Showa sauna had drifted into a hot, dry, endurance-minded Japanese style, today's bathers seek loyly, the burst of steam from water poured over hot stones, the humid Finnish way. Japan's first loyly service is said to have begun at a Sapporo facility in the 1980s, and in the late 1990s New Japan, a venerable sauna in Namba, Osaka in the corporate lineage of the company behind Capsule Inn Osaka, opened the way for its spread through the cities. The service derives from the German Aufguss, yet the story goes that it was deliberately named loyly out of respect for Finland. Today the question of self-service loyly shapes how people choose where to bathe, and saunas that call themselves Finnish-style keep spreading across the country.
The smoke of the stone bath, the steam of the Zen temple, the vapour of Ginza, the heat of the Olympic village. Follow the history of sauna in Japan and you find that what arrived from Finland and what was already on these islands have met again and again. To sit silent in the steam, to sweat, to tighten the body in cold water, to return to stillness. Finland has called this practice sauna; Japan has called it furo. Beyond the difference in names, the two cultures of steam have been answering each other all along. By a lakeside in Helsinki, in a back-street building in Tokyo, people close their eyes in the heat in just the same way.