Hot spring and sauna, all to yourselves

koti hakone has a large bath fed by a free-flowing natural hot spring (onsen), plus a Finnish sauna out in the garden. Since the whole house is yours, you'll never share them with other guests. Use them whenever you like, from check-in to check-out.

The tub and washing area of the large bath

Free-flowing natural hot spring

Sengokuhara Onsen (仙石原温泉) water flows into the tub of the large bath 24 hours a day. Because it's free-flowing, it can't be turned off, so you can soak anytime. The water is classified as a simple spring (hypotonic, weakly acidic, high-temperature). It's colorless and clear, with a gentle level of dissolved minerals.

• The bath has three showers, and the tub is big enough for several people at once
• The water leaves the source at 61°C but cools on its way here, reaching the tub at around 42°C. Depending on the season and weather it can run hotter or cooler, so we've added a faucet at the spout that lets you add cold or hot water. Set the temperature with the lever on the left, then turn the dial in the middle to start the flow
• The changing room has bath towels and face towels for everyone in your group, plus shampoo, conditioner, body wash, face wash, toner, body lotion and makeup remover
• Toothbrushes, combs, body scrub towels and cotton pads are yours to take home. Please bring your own pajamas

Hot spring data

What makes this water special

Based on the components listed in the official hot spring analysis report, the water has these qualities:

• Weakly acidic, like your skin: At pH 3.6 the water is weakly acidic. The surface of human skin is also weakly acidic, so this type of water is said to be gentle on the skin's barrier and easy to bathe in every day
• A gentle simple spring: It contains a mild 456 mg of dissolved components per kg and is "hypotonic," meaning less concentrated than body fluids. It's said to be low in irritation and easy for everyone from children to older guests
• Contains metasilicic acid: The water contains 162 mg per kg of metasilicic acid, which is said to help keep skin moisturized
• Relaxing for body and mind: Simple springs are said to help with autonomic nervous system imbalance and insomnia (according to the indications by spring type in the hot spring analysis report). It's ideal for a soak after the sauna or before bed

Effects vary from person to person.

The washing area seen from the front, with three showers in a row The faucet at the tub spout: left sets the temperature, middle adjusts the flow

Tips for big groups to bathe without waiting

The large bath isn't divided by gender, so most groups take turns by time slot. With a big group, we recommend splitting things up like this:

• Shower room (paid, ¥4,400 per night): A private shower room for one person, with its own washbasin. It can be used at the same time as the large bath and suits anyone who'd rather not bathe in front of others (please bring amenities over from the large bath)
• 2F washroom: It has two washbasins and two low-heat hair dryers. There are also two hair dryers in the 1F changing room. Together with the two washbasins at the large bath, getting ready after your bath won't get crowded
• Nearby day-use hot springs: Such as Sengokuhara Shinanoki Ichinoyu (仙石原 品の木 一の湯, an 18-minute walk) and Susuki no Hara Ichinoyu (ススキの原 一の湯, a 29-minute walk). They give priority to their overnight guests, so please call ahead to check that they're open

Changing room and towel shelves Toothbrushes, combs, cotton pads and body scrub towels on the shelf Skin care products in the changing room Hair dryer in the changing room Shower room Two washbasins on 2F

Finnish sauna

At the back of the garden stands a barrel-shaped Finnish sauna. It uses a 6 kW heater from Harvia, a highly regarded brand worldwide, and heats up to 110°C. You can also do löyly (pouring water on the sauna stones).

The sauna at night

Resting in the fresh air while listening to the sounds of the forest is a pleasure you won't get at a city sauna. Because the sauna and cool-down deck are outdoors, they can be used until 9:00 pm.

Inside the sauna, with the heater Sauna and cold plunge Resting on the cool-down deck (at night)

How to use the sauna

1. After booking, buy the sauna for the number of nights you're staying using the shared payment link under "Paid extras" in the Stay Guide
2. Once payment is complete, the door code for the sauna will be sent to the email address you entered (if it doesn't arrive, please check your spam folder)
3. Switch on the power at the controller in the sauna room 1 to 1.5 hours before you want to go in
4. Bring your own swimsuit and enjoy

Once paid, the fee can't be refunded, even if you don't use the sauna. If 10 sets of towels aren't enough, please purchase one more.

Hot spring and sauna in winter

Winters in Sengokuhara drop below freezing, and the air turns crisp and clear. A soak in the hot spring when you're chilled, and a fresh-air rest in the cold outdoor air, are at their best in winter.

• There's a kerosene heater in the changing room
• To prevent condensation, please keep the large bath's ventilation fan on, even while bathing
• In winter, it can take about 2 minutes for hot water to come from the water heater
• If you're driving, please make sure your car has winter (studless) tires (see Getting here for details)