A wooden bucket, a low stool and a run of taps at knee height come before any water deep enough to sit in. That single fact, that washing happens before bathing and away from the bath itself, is the one piece of etiquette a first-time guest most needs settled before anything else. An onsen is a bath fed by a natural hot spring, defined under Japanese law by the temperature or mineral content of the water at its source, not by the building around it. A sento, the everyday public bathhouse still found in most Japanese cities, runs on ordinary heated water and asks the same manners without the geology behind them. A ryokan's own private tub, filled for one party at a time, may or may not be drawing from a spring at all. The manners barely change across the three: undress completely, wash first, keep the small towel out of the water, and leave the bath itself for soaking rather than cleaning. Everything below is that instruction, worked through in the order a guest actually meets it.
what it is
What an onsen actually is
Japan's Hot Springs Act sets the line precisely. Water counts as onsen if it emerges from the ground at twenty five degrees Celsius or warmer, or, failing that temperature, if it carries a specified concentration of one of nineteen designated minerals, sulphur and iron among them. A sento has no such requirement and no interest in claiming one; it heats ordinary water for residents without a bath of their own at home, a use that has thinned over the decades without disappearing.
A ryokan's private tub sits between the two. Some are supplied from a licensed spring by pipe or by tanker and are onsen in every legal sense; others are simply well-made baths filled with heated water, and the difference is disclosed rather than obvious from looking at it. The private tub in a Kyoto ryokan room, and how that provenance is actually checked, is its own subject, told in full in The Room with Its Own Onsen: Kyoto. What follows here is simpler: what happens once a guest is standing in front of any of the three, spring-fed or not.
An indoor bath and an outdoor one, a rotenburo, are often drawn from the same source inside a single building, and the choice between them is a choice of temperature and air rather than of water. The indoor bath holds its heat more evenly and suits a short, deliberate soak. The outdoor one loses warmth to the air faster, which is exactly why a cold morning or a light snowfall is when it earns its reputation, the body warm and the face cold at the same time.
the order
The order everything happens in
The sequence barely varies between a mountain ryokan and a city sento, and once learned it asks nothing further of a guest, ever again.
- Shoes come off at the entrance, left in a locker or on a low shelf, and go no further than that point.
- In the changing room, everything is undressed and folded into a basket or locker; nothing goes into the bathing area except the small hand towel.
- That towel is for modesty on the walk to the bath. It can be folded on the head or set on the side of the tub, but it never goes into the water.
- Long hair is tied up or wrapped, kept clear of the water entirely.
- Before any bath is entered, the body is washed sitting at one of the low stations along the wall, soap and shampoo rinsed off completely.
- Entry is slow, feet first rather than a straight step down; the water often runs above forty degrees Celsius, and it rewards patience.
- Ten to twenty minutes is a reasonable stay, longer only once acclimatised. Swimming, diving and vigorous movement have no place here, and neither does a phone, anywhere near the water.
- A cold plunge or a sauna, where the building has one, follows the hot bath rather than replacing it; the two alternate rather than compete.
- Before returning to the changing room, the body is dried at the edge of the bath with the small towel, so the floor beyond stays dry, and the minerals left on the skin are not rinsed off again straight away; letting them sit for a while is exactly the point.
Getting dressed again, in a ryokan, usually means a yukata rather than the clothes left behind that morning. It closes left side over right, the same direction as a kimono; right over left is kept for dressing the dead, and Japanese staff notice the reversal instantly even when a guest does not. The sash sits at the natural waist in a simple bow rather than a formal knot, and the whole garment is built to move rather than to be arranged once and left alone.
what a body brings
What a body brings into the water
Tattoos remain the sharpest edge of the etiquette. Most onsen still refuse a visibly tattooed guest, a policy rooted in the old association between tattooing and organised crime rather than in anything about the water itself. The refusal is softening. A number of properties, particularly in resort towns used to guests from abroad, have dropped it altogether, and the Japan Tourism Agency has for some years encouraged operators to reconsider a blanket refusal. None of the properties that have relaxed the rule is named here, because the position still shifts town by town and season by season. A waterproof cover sticker, sold at almost any drugstore, satisfies many of the remaining holdouts for a tattoo smaller than a palm. For anything larger, or for certainty rather than a guess, a private bath, kept for one party at a time, removes the question entirely.
Mixed bathing, konyoku, was once the ordinary case rather than the exception. The segregated bath is largely a Meiji era adjustment, adopted as Japan opened its ports and began measuring itself against a foreign idea of modesty. What survives today is rare, confined mostly to a handful of mountain ryokan and older bathhouses that kept the custom deliberately, and it carries its own quiet rule: a guest does not stare, and many such baths now offer women a wrap or bathing dress the original custom never needed.
Children bathe with a parent of either sex up to about six or seven years old; most prefectures converged on that same line only by 2025, having previously set it as high as ten in places. Past that age, a child goes into the bath that matches their own gender, not the accompanying parent's. During a heavy flow, custom holds that a guest sits that particular bath out, a courtesy to water everyone else is about to share rather than a rule enforced at any door. A private bath removes both questions at once.
The one caution worth stating, once and plainly: a heart condition or high blood pressure calls for a shorter, cooler soak, and no onsen is entered straight after a heavy meal or a large drink. A cup of water before and after the bath replaces what the heat draws out. The light-headedness some guests notice on standing after a long soak is common enough to have its own word, yu-atari, and it asks for nothing more than a seat, a rest, and a second cup of water.
The signage rewards a small vocabulary rather than fluency. 男 marks the men's side, 女 the women's. 湯, painted alone in red over a doorway or curtain, means hot water and is the oldest, plainest sign an onsen has. 露天風呂 names an open-air bath, usually the one worth stepping outside for. 貸切 marks a bath reserved for one party at a time, the private option that answers most of the questions above simply by removing them.
why a ryokan
Why a ryokan is where all of this settles
None of the above quite explains why any of this matters, and the closest answer is a ryokan, where the bath is not a single event but a rhythm repeated across one stay. It is taken before dinner, while the kitchen still has an hour of work ahead of it, to settle a day of walking into something the body is finally ready to sit still for. It is taken again at night, later than seems reasonable, once the corridor has gone quiet and the water has had the whole evening to hold its heat. And it is taken once more before breakfast, when the light through the steam is the only remarkable thing left to notice before the day properly starts. Between the three, the garden beyond the glass keeps changing, evening to full dark to first light, without the guest ever having to leave the building to notice it.
A bath taken three times in one stay stops being a task and becomes the shape of the day itself.
That is the case the old idea of a hot spring stay was always making, without needing to count out ten reasons for it: a guest who has washed correctly, entered slowly, and returned to the same water at three different hours of one day has done something no single visit to a bathhouse can offer, which is to let the water set the pace of a stay rather than interrupt it.
