Did Japan's sauna market actually expand after 2020, or did an already-serious niche simply become louder and more photographed? That is the more useful question, and the one this piece takes up with structure rather than anecdote.
The account below draws on facility-count data I have tracked since 2019 and published in Japanese-language market reviews, cross-referenced against the cultural events any observer of the period would recognize — the 2019 television adaptation of the manga Sadō, most notably. My reading is that of a market participant rather than a neutral outsider: I have advised sauna operators on growth strategy for most of this period. That should be disclosed up front, and it is the reason the emphasis here falls on numbers that can be defined and dated rather than on impression.
The quiet base
Before 2020, Japan's sauna facilities ran on a specific technical default: dry heat and low humidity. Self-service löyly — the Finnish-derived practice of pouring water over the stove's stones yourself — was close to nonexistent: a search of facility listings from the period turned up fewer than forty advertising it, against an industry numbering in the thousands. The cold plunge followed the same restraint: water was often tepid, a formality between rounds of heat rather than a deliberate half of the cycle, inside a sento (neighborhood public bath) treated as everyday infrastructure rather than an experience. Aufguss, the German-rooted ritual of choreographed towel-waving, and the neppashi (heat-wave master) who performs it, already existed in this period, but neither operated at any scale beyond a handful of dedicated facilities. It was a real culture. It was not yet a defined market.
2019–2021: the chain reaction
The shift did not start with an industry decision. Its most visible trigger was a comic: Sadō — "The Way of the Sauna," Katsuki Tanaka's manga about the ritual and philosophy of sauna bathing — had built a readership for years before it reached the platform that mattered: a television drama adaptation in 2019. Sadō functioned as an amplifier, not a sole cause. It gave an existing practice a vocabulary — totonou (the state of deep clarity that follows a full sauna–cold–rest cycle) went from an insider's term to something colleagues could say to each other and be understood — and vocabulary is what let variety shows, lifestyle media, and corporate sauna promotions build on the culture at speed.
What followed is visible in the tracking numbers. Facilities listing self-service löyly went from roughly 37 in early 2019 to 731 by January 2022, and to 1,347 by that November — listings, not construction counts, from a search run against Sauna Ikitai, Japan's largest facility-review platform, whose own coverage also grew over the same period. The shift accelerated through the pandemic years, when outdoor and private sauna formats were among the few leisure categories still open under Japan's pandemic-era restrictions.
Three structural shifts inside the room
Put the timeline aside and look at what physically changed inside a Japanese sauna, because this is the part general coverage of the boom tends to skip.
Self-service löyly went from prohibited to expected. The listing count above traces that reversal.
The cold plunge became a genuine engineering investment. Chillers, better insulation, and a wider industry recognition that the cold side of the cycle is half the experience, not a formality, have replaced the tepid plunge at the facilities leading the boom with water kept genuinely cold. Chiller installation is now one of the more expensive line items in a modern sauna build-out.
Aufguss moved from a niche service to the center of the room. As the audience widened, so did demand for intensity — not just heat to sit in, but heat as performance. Aufguss and the neppashi who leads it went from a fringe offering at a small number of facilities to a headline draw at flagship venues, with sessions now scheduled, timed, and marketed much like a live show.
A market with a definition
Three structural changes converged, in my reading, into something the pre-2020 market didn't have: a common competitive specification. Among the newer destination facilities, competition now runs, in large part, on the same three axes — a room that reliably gets and holds heat, a plunge that is genuinely cold, and a löyly or Aufguss program that turns the middle of the session into something closer to choreography than endurance. That trinity did not operate as a shared standard before the boom; operators competed on ambience or heritage. Now they also compete on a specification.
The numbers above are a practitioner's field tracking — compiled by the author, published in Japanese-language market reviews, checked where possible against public search-index tools — not an independently audited market report. Whether the underlying user base actually expanded, or an already-serious niche simply became more visible, is a question these metrics don't settle. Verifying that claim — across the full data set, the methodology, and the user base — is the work taken up in the author's ongoing Japanese-language market analysis, published on note.
None of the above needs to stay theoretical for a visitor. Go in quiet, watch how regulars move before you move, and give the full cycle — heat, cold, and whatever form of löyly or Aufguss the house runs — a real chance before deciding what you think of it. The room described in the first section of this piece still exists in places. The newer model now runs alongside it — and it is the one worth booking a trip for.
— Takayama Sauna, Editor-in-Chief
Lead photography by Anne Nygård on Unsplash.