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  • Writer's pictureDia KL

Onsen introduction: the Japanese hot springs

Updated: Jan 3

Sulfuric outdoor onsen (hot spring) with blue water in Beppu, Oita Prefecture, Kyushu, Japan
Private outdoor sulfuric onsen

After spending some time in Japan I became a big fan of onsen, the Japanese hot springs. To be honest, before coming to Japan for the first time as a backpacker in my early 20s, I also thought that the hot spring is just a place with nice hot water for you to relax. But with the passage of time I realized that there is so much more in it, so much depth. Now I am so much into it that I am always looking for new onsen to bathe in.

Outdoor onsen with a mountain view in Yufuin, Oita prefecture, Kyushu, Japan
Public outdoor onsen with a mountain view

I have been thinking for quite some time to start posting about various onsen I visit whenever I am in Japan. But before I start posting, I needed to make an introduction, as the hot spring experience in Japan is probably a little different than other countries. There are manners and unwritten rules to follow which usually the first-timer is totally unaware of... I could write endless pages about the onsen but I will do my best to keep this as brief as possible.

Historically, onsen was mentioned as a purifying ritual in the Japanese religion Shinto and for the enjoyment of the emperors. Eventually it spread across the country for everybody to enjoy. It is written 温泉 which literally means "hot spring". Sometimes the symbols ♨ or 湯 (hot water) or ゆ ("yu" sound, for hot water) are used as well. It shouldn't be confused with the "sentou" (銭湯) which is a bathhouse with common heated water.

Outdoor onsen in Kuju mountains, Oita prefecture, Kyushu, Japan
Private outdoor onsen with a mountain view

Japan has around 27.000 onsen (the exact number is hard to calculate) all around the country. There are 10 different kinds of hot spring water that exist in the world (simple, acidic, alkaline, sulfur, iron, carbonated etc.). Various minerals (calcium, chloride, sodium, sulfate, magnesium, iron, silica etc.) are mixed in their waters. They exist in many kinds of locations and scenery and might have various forms. It might be a communal neighborhood onsen with a tiny tub where you will meet all the locals or in a luxury hotel with multiple tubs and sauna. It could be in a temple, a restaurant, a greenhouse, somebody's private home and all kinds of other crazy places. It could be public, private, only for members. It could be indoor, outdoor or even wild in nature. Could be up in the mountains, next to the sea, next to waterfalls, next to a volcano crater, inside a cave, even inside a river! The onsen water will have different kinds of colour, smell, taste and temperature. It could be a normal onsen to soak your body but it could be just for your feet, other times a sand spa, a steam spa or even a mud spa. In some cases you can even drink the hot spring water!

Depending on all the above factors (and many more) every onsen will have different therapeutic effects to your body. Depending on the minerals, there might be various particles inside the water or different colour stains on the floor and walls, it is not dirty! How you behave in the onsen is called "onsen manner" which has various rules which I will try to summarize bellow, offering some more information about the experience at the same time.

Private indoor onsen cooking pot style, Oita city, Oita prefecture, Kyushu, Japan
Private indoor onsen cooking pot style

*Entering the premises

In Japan you always take off your shoes before you enter a house, of course it is the same with the onsen. If it is a small place you will see where the other people have left their shoes. If it is a big place it will have a designated place at the entrance and even shoe lockers sometimes. If it is wild in nature you still can't go with your shoes, you will find a place where you leave them.

*Greetings to locals

It is customary to greet the locals, both in the changing and bathing area. A simple hello (konnichiwa) or good morning (ohayou gozaimasu) will do the trick. You greet them once more when you leave (leaving from the tub to go change, exiting the premises etc.). Again a simple word would be fine, something like goodbye (sayounara), goodnight (oyasumi nasai) or thank you (arigatou gozaimashita). If you feel like impressing the locals you could say the proper line when you leave a place in Japan which would go like "osaki ni shitsurei shimasu" followed by your greeting (goodbye etc.). It is kinda hard of explaining the meaning of this phrase but a translation would be "excuse me for leaving before you". The greetings are especially important if you visit a local public onsen. In the big facilities or hotels you might notice people not greeting each other or that -rarely- you might greet and not get a response. You should try to greet either way.

Indoor public local onsen, only for members, Beppu, Oita prefecture, Kyushu, Japan
Public indoor local onsen, only for members
Indoor public local onsen, Beppu, Oita prefecture, Kyushu, Japan
Public indoor local onsen

*No clothes, completely nude

Yes, you bathe the same way you were born, nude. No clothes or swimming suits are allowed. Unless you are in a private onsen (which means you will bathe alone or with your companions), you will be bathing with other people which you have never met in your life.

Almost all the onsen nowdays are sex segregated, male and female, make sure you don't enter the wrong place! That said, there are a few (mostly local) places that the onsen is mixed, men and women will bathe together, of course nude. An interesting note, before WW2, a high percentage of the onsen in Japan were mixed. Gender separation has been enforced since the opening of Japan to the West and Western culture. But in a few places where the onsen culture is still strong, you might find mixed onsen where people are bathing all together, as they used to do in the past. Kids accompanied by their parents can bathe in any of the two, don't be surprised if you see a little boy bathing with you in the female section and vice versa. LGBT have to choose male or female section as well, unless they go to a private onsen.

Some onsen have lockers for your valuables and clothes, the more local ones don't. People rarely steal in Japan so it is usually safe but you could place your stuff somewhere that you might be able to have a look while bathing (some times). Finally there are very few rare cases that you will be instructed to put a swimming suit on, for example if the onsen has some kind of pool facility with onsen water.

Mixed outdoor public onsen in a river! Taketa, Oita prefecture, Kyushu, Japan
Mixed public outdoor onsen in a river!
Mixed outdoor onsen up in the mountain, next to a stream. Beppu, Oita prefecture, Kyushu, Japan
Mixed public outdoor onsen up in the mountain, next to a stream
Mixed outdoor public onsen. Oita prefecture, Kyushu, Japan
Mixed public outdoor onsen

*Washing your body and cleanliness

When you enter the onsen tub to bathe you must always be clean. That means washing your body and hair before entering. Some onsen provide an area with shower heads, and stools to sit and wash up. In the more local ones or the wild ones in nature, you simply sit on the ground next to the tub and use a little bucket to pour water on your self. You must be careful not to accidentally throw any soap inside the tub or the people who are washing themselves close to you. Further more you must be careful with the water, not to splash on anybody else, both when you use the bucket to take water from the tub and when you pour it on you, that is why you always wash yourself sitting and not standing. After you have finished cleaning yourself, make sure there is no more soap on your body and you can enter the tub.

You might see some locals that instead of washing themselves, just do "kakeyu", which means dousing themselves with just onsen water outside the tub or even sometimes only at their private parts, and enter the tub. They might have been to another onsen before that, they might feel that clean, who knows. We, as foreigners, should do the proper bathing ritual, even if we feel clean. Another note is that swimming suits are not allowed in the onsen because they are considered dirty. Not to mention that it could get really ruined in some types of water.

If the onsen has a sauna, you will need to wash off your sweat before you go back to any tub, there is usually a cold tub for this purpose, you first wash off your sweat with a bucket outside the tub and then you can have a nice refreshing cold dip.

*Shampoos and soap

Some onsen offer shampoos for free in the bathing area, some don't have at all, this is usually the case with the very local ones. In this case you need to have your own shampoos with you. There are a few cases that shampoos are not allowed (for example when the drainage of the onsen goes straight to a river etc.), there will be a sign about it and then you are expected to do a really good "kakeyu" (explained above). Some onsen sell single use shampoos, soaps, razors to shave, towels etc.

Onsen pool on a hotel, here you bathe with swimming suit and have nice views over the town. Beppu, Oita prefecture, Kyushu, Japan
Mixed outdoor public onsen pool on a hotel, here you bathe with a swimming suit

*Towel and getting out of the tub back to the changing room

A towel is usually not provided, apart of the more upmarket onsen. The same with the shampoos, you bring your own.

You must make yourself dry BEFORE you go back to the changing room. This means that you need to take your towel with you inside the bathing area. Your towel can't be left anywhere while you are bathing and it should never touch the water. If you have brought your own shampoos you will probably have a little bag or as the locals do, a little plastic basket, you can have your towel in there. Traditionally, the Japanese use their towel as a washing sponge for their body. This means their towel is quite small (for Western standards), almost the size of a face towel, and much thinner. They soak it wet, add the soap, scrub their body and then rinse it clean. They squeeze it dry and then they can dry themselves.

You might see some people placing their towel on their head while bathing. If you do that, be careful not to drop it in the water. In the male section, sometimes you might see some guy covering his genitals with his towel while walking around, it is considered more polite. I don't usually do it, unless I see everybody else doing it. Getting out of the tub and straight to the changing area being dripping wet is very much frowned upon!

*Long hair

If we have long hair we tie them in a way not to touch the water while bathing. We don't submerge our head inside the water.

Public outdoor onsen in front of the sea, Hiji, Oita prefecture, Kyushu, Japan
Public outdoor onsen in front of the sea

*Noise and alcohol

The onsen is a place that you go to relax and not have fun. So you don't make noise, of course you can strike a conversation if the people bathing with you are into it (the elder folks are usually curious about you), but still in a relaxed manner and without shouting. You don't splash in the water, swim or dive. Alcohol is not allowed in the onsen mostly because the combination of onsen and alcohol can be dangerous, plus the locals don't want to have drunk noisy people bathing next to them. Children might be allowed to do a bit of noise and playing around.


Many onsen unfortunately don't allow people with tattoos to bathe. The origin of this ban goes way back to the times when the onsen facilities were trying to forbid the yakuza (Japanese mafia) from entering and harassing people. Yakuza usually have -beautiful I personally think- full body tattoos. But these days, where having a tattoo is absolutely normal, this ban might be a bit too far. It is true that some Japanese still feel unease having somebody bathing next to them with tattoos, so if some onsen has a no tattoo sign you usually can't do anything about it, unless they have a private bath. But if it's a small one you might manage to cover it up with some plaster. On the other hand, the number of onsen that allow tattoos is growing.

No tattoo sign at the entrance of a public onsen, Oita city, Oita prefecture, Kyushu, Japan
No tattoo sign at the entrance of a public onsen
No tattoo sign at the entrance of a public onsen, Oita city, Oita prefecture, Kyushu, Japan
No tattoo sign at the entrance of a public onsen

*Entering the tub

Be careful, especially if you are a beginner. The water temperature can be as hot as 47°C but it is usually the minerals that make it really strong, even in lower temperatures. Kakeyu (mentioned above) is a good way to acclimatize yourself with the water temperature. Submerge yourself slowly without splashing and don't spend too much time in the water, at least for the start. A few minutes would do, go out to take a little break and back in. If you feel dizzy, like fainting or your heart is pumping fast then go out and have a break. Many people get dizzy as soon as they stand up to get out of the tub, in this case just go out and stay low for a while, even sit on the ground maybe. Needless to say that if you faint you might get injured or worse, if you are alone you could even drawn!

*Adding water to the tub

If the onsen is too hot, there is usually a way to to cool it down a bit. You should always ask the locals before you try to change the water temperature. Most of the times you can add cold water, some other onsen can cut the supply of hot spring water as well if needed. Never mess up with any lever you don't know and never remove the cap to the drainage (unless instructed, in rare cases).

Illustration of the onsen manner rules, inside a public indoor local onsen. Beppu, Oita prefecture, Kyushu, Japan
Illustration of the onsen manner rules, inside a public indoor local onsen
Onsen chart paper with information about the quality, minerals and temperature
Onsen chart paper with information about the quality, minerals and temperature

Finally, some more technical information, written as simplified as possible. In Japan people care not only in what kind of water they are bathing, but also where and how the water comes from. There are two different categories, with four indications total, which are important.

  1. GENSEN: the onsen facility has the source fountainhead in its premises.

  2. HIKIYU: the onsen is supplied with water thought a pipe from a source fountainhead somewhere out of the premises.

  • a. KAKENAGASHI: the onsen is supplied with water directly from a fountainhead and does not recycle it's water, discharged water that overflows from the tab goes to the drain.

  • b. JYUNKAN: the onsen is supplied with water by a circulatory system which reuses the discharged water after filtering the chlorine which is used for disinfection.

The two categories can get mixed, so you can have (1a) gensen kakenagashi, (1b) gensen jyunkan, (2a) hikiyu kakenagashi, (2b) hikiyu jyunkan. Most people prefer (1a) gensen kakenagashi, as the natural hot spring water that flows to the bath has, until that point, not come into contact with the air. Therefore it has the original color, smell and texture of the water - when water makes contact with the air it gets oxidized and might change its characteristics. On the other hand, in an onsen that its source doesn't provide enough water for continuous flow or the amount of people bathing is very large, then (b) jyunkan might be needed in order to keep the water clean.

The most important is to relax both your mind and body, and enjoy being naked alone or with other people soaking in the hot water. Bathing in the onsen is part of Japanese life and a unique experience which you shouldn't miss out by no means when visiting Japan!

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