Japan Hot Spring Guide: Types, Best Regions & Onsen vs Sento

What Is a Japan Hot Spring? Onsen vs Sento vs a Hotel Bath

An onsen is defined by law as a hot spring. As per Japan's Hot Springs Act of 1948, the water must either come out of the earth at a temperature of at least 25°C or contain certain substances in specific amounts. 

More than 19 substances have been identified, and one of those regulations states that there must be at least 1,000 mg of dissolved minerals per kilogram in the water.

The term also refers to the bathhouses and inns constructed around the spring, which explains why "onsen" can denote the water itself, the bath, or the entire town.

Two things are commonly confused with onsen:

Sento

A public bath within a residential area that heats up ordinary tap water. It is generally cheap and regulated: the maximum average price for an adult in Tokyo rises to ¥600 on 1 August 2026, while the national average for adults is around ¥478. There are also gigantic super sento spa complexes, which are not subject to the same price caps and usually charge from around ¥1,000. Some sento use real hot spring water and are known as onsen sento.

A Hotel with a Hot Tub or Large Bath

Most business hotels offer large communal baths that emulate onsen but use ordinary water from the main instead of natural hot spring water. While they can often be relaxing, they do not actually count as onsen.

How to tell the difference

A proper onsen should be displaying its spring analysis certificate (温泉分析書) at the reception, as mandated by law. This shows the temperature of the spring where it was sourced and what minerals it contains. Hotels that have real spring water piped in usually state this in their introduction. 

The water varies in each of the springs. There are ten types of water in Japan, which are officially recognised. For example, chloride (salty and warm), sulphur (associated with the bad smell of rotten eggs, found in Kusatsu and Noboribetsu), iron (yellowish, as in Arima), and radon (in Misasa). Luckily you do not need to memorise this list, as the onsen itself will tell you what type of water it is!

Types of Hot Spring Baths in Japan: Outdoor, Indoor, Private and Foot Baths

Most onsen offer several bathing formats under one roof, so you can try more than one during a single visit.

The waters themselves can be broadly divided into two categories. 

The first is a free-flowing bath where fresh spring water is constantly replenished and allowed to overflow. 

The second category encompasses baths where water is recirculated, filtered and cooled (by adding water or reheating), which tends to be found at larger hotels and at sources which are below 25 degrees C or too hot to bathe in directly. 

Both are perfectly legal, and both are onsens so long as the source it was taken from meets the criteria. 

Should freshness be of concern to you, then look for a specification of 100% free flowing in the hotel's description.

Japan Hot Spring Etiquette: How to Use an Onsen Correctly

The bath is shared water, so almost every rule exists to be clean and not disturb others. So follow this order to blend in.

• First, take off everything and put it in a locker. Baths are divided between men and women, and you must bathe nude. Swimsuits typically aren't permitted at traditional onsen.
• Next, take a small towel with you and use it to cover your privates on the way and then fold it on your head or on the edge of the tub, never to put it into the water.
• Then, wash while sitting down at a shower located near the bath. Shampoo and soap, then rinse off all the soap. This is the most important rule.
• Make sure to tie up your hair to keep it from getting into the water.
• Also, rinse off with a few scoops (about three to five) of bath water to let your body temperature adjust.
• Finally, sit down and relax, but be quiet; don't swim around or take pictures, and dry off completely before returning to the changing room and drinking water to replenish.

Tattoos

Many onsens are traditionally not allowing people with tattoos, due to their association with organised crime. This depends on the establishment, however, so it's best to check ahead of time. Larger resorts or those geared toward tourists may be more accommodating. 

• Some allow small tattoos, often ones that can be covered by a sticker (many convenience stores and drugstores sell them), or outright prohibit tattoos. 
• Private baths, where you are either entertaining yourself or your own party, are usually safe, as there is no one else to potentially offend. 
• It is always best to contact the establishment in advance if you aren't sure, especially if it isn't readily apparent.

Staying safe

• Wait for 30 to 60 minutes after a long trip, and do not bathe after drinking alcohol or immediately after a heavy meal. 
• The Japanese Ministry of the Environment advises that people with heart conditions or high blood pressure should be especially cautious. 
• Limit each session to about 10 to 15 minutes, and take care not to stay in hot water too long if you are prone to feeling faint. Rinse off before getting into bed. Have a drink of water before and after your soak. 
• Settle down with a beer after you finish.

Best Hot Spring Towns and Regions in Japan, by Region and Season

Japan has approximately 3,000 onsen, so we recommend choosing your region first and then the season. 

Autumn and winter are the best times for an outdoor bath, while spring is perfect for bathing amidst cherry blossoms, and in summer, it's best to head to a high altitude such as Kusatsu town.

If you have time for only one area in Tokyo, choose between Hakone and Atami; from Osaka or Kyoto, pick between Arima for a day-trip or Kinosaki for an overnight stay; and for a rural-based excursion that's worth taking away from the big cities, consider Kurokawa or Noboribetsu (both are longer drives). Be sure to check with the ryokan about hours of operation, tattoo policies, and day-bath availability.

Day-Use Onsen vs a Ryokan Stay: Two Ways to Experience Japan Hot Springs

Day-use baths (higaeri) 

These allow you to relax without having to spend the night. Public bathhouses and many hotels and ryokan offer entry for a few hours (typically late morning to early evening) for a payment at the time of your visit. 

You will need to bring (or rent) a towel, and note the final entry time, which can be an hour or more before closing. 

Some inns close their doors to day visitors on weekends and holidays and on days when special events are taking place, so it's a good idea to call ahead on the day you plan to visit. This is the best option if you're based in Tokyo, Osaka or Kyoto, as Hakone, Atami and Arima all make excellent day trips.

An overnight ryokan stay

This is the fuller experience. You sleep on futons on tatami, change into a yukata, bathe in the evening and again in the morning, and eat a multi-course kaiseki dinner (often served in your room) and a Japanese breakfast. 

Prices are quoted per person with two meals (1泊2食), not per room. If you are travelling with older parents, young children or a tattoo, ask for a room with its own bath.

For your first trip, a sensible plan is one day of soaking nearby, staying in a hotel close to the city base, and one night, one ryokan (traditional Japanese-style inn), in a more subdued setting. 

If you can only stay for one night, it's best to pick a weekday, as weekends, holidays, and peak seasons will see prices increase significantly.

Getting There and Accessibility 

Reaching rural onsen towns

Hakone is around ninety minutes from central Tokyo, while Atami is just forty-five minutes by Shinkansen bullet train from Tokyo Station. It is advisable to take the local Kinosaki station. The Kounotori limited express train from Osaka takes around two hours and forty minutes (approximately ¥6,140), and the highway bus takes around three hours and forty (around ¥4,100). 

Kurokawa does not have a train station at all. Buses depart from Fukuoka and take around three hours (approximately ¥3,470), and also there are buses leaving from Kumamoto in around two hours and forty minutes with another bus ride of approximately fifty minutes from JR Aso station. Departures are irregular, so it is essential to check the last buses back before exploring the area on a day trip.

Older visitors and accessibility

A private bath or one inside your room provides reassurance that you will not have to contend with crowds, stairs, and undressing in front of others. Many ryokan offer barrier-free rooms, and others have handrails, bathing wheelchairs, or lifts in their main baths.

In Kinosaki some ryokan are equipped with accessibility features, and the loop bus in Hakone has wheelchair lifts (although it tends to be crowded). 

Ensure you ask about stairs when making a reservation and how far you have to walk to the nearest station since the images can mislead you regarding the steps. 

Also, older guests are advised to not spend too much time in the bath due to medication that they might be taking for blood pressure.

Families

Children are welcome, and many bathhouses offer children discounts, like around ¥500-1,100 for ages 4-12 at some day-use places. 

A family bath offers the chance for everyone to stay together.

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