Acidic Springs: Strongly Antibacterial Waters & Their Skin Indications

This unique created hot spring utilizes the fumaroles of Owakudani, which were formed by volcanic activity approximately 3000 years ago. In the early Showa period, Hakone Onsen Kyokyu Co., Ltd. developed this source to supply hot water to areas like Sengokuhara and Gora. The water, created by mixing volcanic gas and water, offers a distinct, tingling, and tightening sensation upon contact with the skin. The powerful energy from the earth delivers restorative warmth deep into the body, a warmth that lingers long after your bath. It is ideal for those seeking deep relaxation and rejuvenation, wishing to refresh their mind and body.

The Oyu source of Shimofuro Onsen carries a sulfur scent so strong that the place name is said to come from the Ainu word "shumafura," meaning "smelly rock." Recorded as "Yumoto" on a Muromachi-period map and bathed in by a Nanbu domain lord in 1656, this pH 2.4 acidic water turns milky as its sulfur flakes swirl, leaving a brisk, tightening touch and a lingering saline warmth. It suits those who wish to steep quietly in a strong sulfur spring within a port town that once thrived as a herring fishermen's spa.

Ubayu Gensen gushes naturally from fissures in acidic welded tuff at roughly 1,250 metres on the flank of Mount Dainichi in the Azuma range. Tradition holds that Endo Okura, a gold prospector, found it in 1533 after meeting a mountain crone — the yamauba whose name the source still carries. Carried down by gravity through vinyl piping and cooled in troughs that harvest sulphur flowers, its pH 2.6 waters bubble with hydrogen sulphide, tightening the skin and leaving a clean lightness behind. It suits travellers who want deep mountain stillness.

Originating from the fumaroles of Owakudani, born from the eruption of Hakone volcano approximately 3,000 years ago, this artificially developed hot spring began to be supplied to Sengokuhara and Gora by Hakone Onsen Kyokyu Co., Ltd. in Showa 5 (1930). Its renowned milky white waters, blended with naturally gushing spring water, offer a pleasant sensation that tightens the skin and a powerful restorative warmth that penetrates deep into the body's core. After bathing, you'll feel surprisingly refreshed and light. It's a perfect companion when you seek to feel the Earth's energy and achieve deep relaxation and rejuvenation for your mind and body.

The Mandaiko source, originating from traces of past mining development, is deeply intertwined with Kusatsu Onsen's unique yumomi culture and its long history of toji (therapeutic bathing). Its highly acidic waters, among Japan's most potent, deliver a distinctive tingling sensation, awakening both mind and body and offering a sense of rejuvenation. The high-temperature blessings penetrate deep into the core, leaving you with a surprisingly light and refreshed feeling after your bath. We invite those seeking a genuine toji experience, a true escape from daily life to restore their mind and body, to discover the profound power of this spring.

The Yubatake source, naturally gushing from Kusatsu Onsen's iconic Yubatake (Kusatsu's central hot-water field), holds a distinguished history. During the Edo period, it was ranked as the highest-ranking Ozeki in the Onsen Banzuke, recognized alongside the Shirahata source as one of Kusatsu's two major hot springs. Its powerful, pH2 water, permeated with a sulfurous aroma, imparts a refreshing, tightening sensation upon the skin. A soak in this historic, renowned hot spring cleanses the body and mind, offering deep relaxation and rejuvenation from daily fatigue. It is a must-visit for those seeking to feel the energy of a historic hot spring and desire a complete refresh.

The Mandaiko source, originating from traces of past mining development, is deeply intertwined with Kusatsu Onsen's unique yumomi culture and its long history of toji (therapeutic bathing). Its highly acidic waters, among Japan's most potent, deliver a distinctive tingling sensation, awakening both mind and body and offering a sense of rejuvenation. The high-temperature blessings penetrate deep into the core, leaving you with a surprisingly light and refreshed feeling after your bath. We invite those seeking a genuine toji experience, a true escape from daily life to restore their mind and body, to discover the profound power of this spring.

Myoban Onsen prospered in the Edo period through alum production and still keeps rows of thatched huts where yunohana sulfur flowers are made. Here the Okamotoya Ryokan source gushes naturally at 74.4°C in Myoban 3-kumi; colorless as it emerges, it turns a milky, bluish white once it meets the air in the bath. Its acidity gently loosens old skin cells, leaving a soft, light feeling afterward, and it suits anyone who wishes to steep in dense sulfur water amid mountain steam.

Nestled in Kusatsu Onsen, one of Japan's three most renowned hot springs, Jizo-no-yu has been cherished since ancient times, deeply intertwined with Kusatsu's unique `yumomi` (hot water stirring) culture. This powerful spring, known for its invigorating touch, seems to cleanse away physical and mental stagnation. It provides a deep, restorative warmth that penetrates to the core, offering a refreshing sensation akin to rejuvenation after your bath. Jizo-no-yu offers solace to travelers seeking relief from persistent fatigue or skin discomfort, and those desiring an authentic hot spring experience.

This rare, naturally gushing source emerges from beneath 'Gensenkaku,' nestled beside Kusatsu Onsen's iconic Yubatake (Kusatsu's central hot-water field). Despite its strong acidity, its waters offer a remarkably soft bathing sensation, akin to being enveloped in silk floss. The milky-white waters, renowned for having Kusatsu's finest 'yunohana' (hot spring minerals), gently embrace the skin, contributing to silky skin and providing a restorative warmth that lingers deep within the body. Known as a 'phantom spring' for its history of disappearing once during the Taisho era, it now offers a profound escape from daily life, inviting deep relaxation and rejuvenation.

Housen-no-Yu, a precious spring at Kusatsu Onsen, one of Japan's three most famous hot springs, has naturally gushed from bedrock for approximately 1200 years. Distinct from major sources like Yubatake and Bandaiko, this rare water gently envelops the skin with its sulfurous aroma. Its crisp quality offers a sensation of purifying both mind and body. After bathing, your skin will feel wonderfully silky, and the restorative warmth from deep within will invite deep relaxation, supporting overall rejuvenation. It is highly recommended for those seeking to escape daily life and reset themselves with a truly special hot spring experience.

The Yubatake source, naturally gushing from Kusatsu Onsen's iconic Yubatake (Kusatsu's central hot-water field), holds a distinguished history. During the Edo period, it was ranked as the highest-ranking Ozeki in the Onsen Banzuke, recognized alongside the Shirahata source as one of Kusatsu's two major hot springs. Its powerful, pH2 water, permeated with a sulfurous aroma, imparts a refreshing, tightening sensation upon the skin. A soak in this historic, renowned hot spring cleanses the body and mind, offering deep relaxation and rejuvenation from daily fatigue. It is a must-visit for those seeking to feel the energy of a historic hot spring and desire a complete refresh.

The Yubatake source, naturally gushing from Kusatsu Onsen's iconic Yubatake (Kusatsu's central hot-water field), holds a distinguished history. During the Edo period, it was ranked as the highest-ranking Ozeki in the Onsen Banzuke, recognized alongside the Shirahata source as one of Kusatsu's two major hot springs. Its powerful, pH2 water, permeated with a sulfurous aroma, imparts a refreshing, tightening sensation upon the skin. A soak in this historic, renowned hot spring cleanses the body and mind, offering deep relaxation and rejuvenation from daily fatigue. It is a must-visit for those seeking to feel the energy of a historic hot spring and desire a complete refresh.

The Mandaiko source, originating from traces of past mining development, is deeply intertwined with Kusatsu Onsen's unique yumomi culture and its long history of toji (therapeutic bathing). Its highly acidic waters, among Japan's most potent, deliver a distinctive tingling sensation, awakening both mind and body and offering a sense of rejuvenation. The high-temperature blessings penetrate deep into the core, leaving you with a surprisingly light and refreshed feeling after your bath. We invite those seeking a genuine toji experience, a true escape from daily life to restore their mind and body, to discover the profound power of this spring.

The Mandaiko source, originating from traces of past mining development, is deeply intertwined with Kusatsu Onsen's unique yumomi culture and its long history of toji (therapeutic bathing). Its highly acidic waters, among Japan's most potent, deliver a distinctive tingling sensation, awakening both mind and body and offering a sense of rejuvenation. The high-temperature blessings penetrate deep into the core, leaving you with a surprisingly light and refreshed feeling after your bath. We invite those seeking a genuine toji experience, a true escape from daily life to restore their mind and body, to discover the profound power of this spring.

Obuki is the roaring source at the heart of the steaming geothermal field of Tamagawa Onsen, on the southern slopes of Hachimantai. Its output from a single vent is often said to be the largest in Japan, and the fumarole field around it has long produced mineral deposits and the rare hokutolite stone. Every bath in the spa draws on this one source, served either straight or cut with fresh water. At pH 1.13 the water tingles sharply on the skin while warming the body to the core, and it has welcomed long-stay therapeutic bathers for generations, a spring for those who want to meet nature at full strength.

Ishida Onsen's source flows naturally on the flanks of Mt. Esan, an active volcano, and is piped about 2.5 km down, inheriting the spring once used by a highland hotel. The 1984 analysis shows pH 2.1 and 5.518 g/kg of dissolved solids, with 2,972 mg/kg of sulfate plus abundant aluminum and iron, in the lineage of classic alum and green-vitriol springs. Clear at the source, the water oxidizes to a cloudy yellow-brown in the bath, with a squeaky feel, sour taste and metallic scent that speak of the volcano.

Dake Onsen's association source feeds a spa village said to have opened in 1674. Its self-flowing water is piped several kilometers down from the slopes of Mt. Iwaki, and the local association flushes sulfur deposits from the pipes every month. Listed in Edo-period hot spring rankings, its sharply sour, sulfurous water suits travelers seeking an old-fashioned toji retreat.

The Mandaiko source, originating from traces of past mining development, is deeply intertwined with Kusatsu Onsen's unique yumomi culture and its long history of toji (therapeutic bathing). Its highly acidic waters, among Japan's most potent, deliver a distinctive tingling sensation, awakening both mind and body and offering a sense of rejuvenation. The high-temperature blessings penetrate deep into the core, leaving you with a surprisingly light and refreshed feeling after your bath. We invite those seeking a genuine toji experience, a true escape from daily life to restore their mind and body, to discover the profound power of this spring.

Obuki is the roaring source at the heart of the steaming geothermal field of Tamagawa Onsen, on the southern slopes of Hachimantai. Its output from a single vent is often said to be the largest in Japan, and the fumarole field around it has long produced mineral deposits and the rare hokutolite stone. Every bath in the spa draws on this one source, served either straight or cut with fresh water. At pH 1.13 the water tingles sharply on the skin while warming the body to the core, and it has welcomed long-stay therapeutic bathers for generations, a spring for those who want to meet nature at full strength.

The Bandaiko source, which unexpectedly erupted from within the Bandai Sulfur Mine in 1970, now stands as Kusatsu's primary hot spring, boasting the largest output and supporting the town. Named with the wish for 'eternal prosperity' (万代), this powerful source was born in the mountains, far from the Yubatake (Kusatsu's central hot-water field). Its colorless, transparent waters deliver a stimulating tingle that awakens both mind and body, while its robust warmth permeates to the very core. This energetic spring is a perfect companion for those seeking liberation from daily routines and a crisp mental and physical rejuvenation.

Nestled in Noboribetsu Onsen, famously called the "Department Store of Hot Springs" and rooted in the Ainu "Nupur-pet" (deeply colored river), the historic "Uma no Yu" source has flowed since Taisho 6 (1917). Its faint sulfur aroma gently unwinds the mind and body. The waters, softly enveloping the skin, warm the body to its core, providing restorative warmth that lingers. Overlooking a beautiful Japanese garden, this tranquil spring offers deep relaxation, a serene escape from daily commotion.

This source rises in Konya Jigoku, a steaming "hell" of Myoban Onsen, one of the Beppu Hatto hot spring areas, where sulfur-rich fumaroles drift over the ground. With pH 2.9 and abundant sulfate, the bluish milky water turns grey in shadow and leaves a crisp, tightening touch on the skin. The scent of sulfur lingers long after bathing, making it a favorite for travelers who love cloudy, characterful waters and a refreshing soak.

This spring rises at a spa retreat about 900 m up the northwest flank of the Hakkoda Mountains, amid beech forest, in the area chosen as Japan's first National Health Resort Hot Spring. It has long filled a great bathhouse built entirely of hiba cypress alongside the area's other springs. At pH 1.71 it is strongly acidic, with a tingling bite on the skin and a faint scent of sulfur and iron; sinking into its milky water feels like the essence of a traditional healing spa, especially in deep-snow winter.

The Taenoyu Onsen (Kin no Yu) source gushes naturally in the gorge of the Sendatsu River that runs through the Nyuto Onsenkyo, and it earns the name "golden water" as its iron shifts from gold to deep brown on meeting the air. At pH 2.9 its acidic water tightens the skin while its sulfates let warmth linger in the body. It suits travelers who wish to restore body and mind in a spirited spring to the sound of the mountain stream.

The Mandaiko source, originating from traces of past mining development, is deeply intertwined with Kusatsu Onsen's unique yumomi culture and its long history of toji (therapeutic bathing). Its highly acidic waters, among Japan's most potent, deliver a distinctive tingling sensation, awakening both mind and body and offering a sense of rejuvenation. The high-temperature blessings penetrate deep into the core, leaving you with a surprisingly light and refreshed feeling after your bath. We invite those seeking a genuine toji experience, a true escape from daily life to restore their mind and body, to discover the profound power of this spring.

The Nuruyu source has been known since the Kyoho era (1716-1735), welling up at about 920 m on the eastern foot of Mt. Azuma-Kofuji. This acidic sulfate water carries iron and aluminum, emerging colorless and turning yellowish-white after a day. Though only 31.8°C, it lets warmth linger slowly in the body, leaving skin cool and smooth. It suits summer bathers and anyone who loves long, unhurried soaks in a water traditionally prized for the eyes.

The Yubatake source, naturally gushing from Kusatsu Onsen's iconic Yubatake (Kusatsu's central hot-water field), holds a distinguished history. During the Edo period, it was ranked as the highest-ranking Ozeki in the Onsen Banzuke, recognized alongside the Shirahata source as one of Kusatsu's two major hot springs. Its powerful, pH2 water, permeated with a sulfurous aroma, imparts a refreshing, tightening sensation upon the skin. A soak in this historic, renowned hot spring cleanses the body and mind, offering deep relaxation and rejuvenation from daily fatigue. It is a must-visit for those seeking to feel the energy of a historic hot spring and desire a complete refresh.

Originating from the dramatic Jigokudani (Hell Valley), the potent waters of Noboribetsu Onsen, a renowned hot spring resort in Hokkaido, have long welcomed those seeking therapeutic benefits. This powerful spring gently envelops the skin, delivering restorative warmth that penetrates deep into the body's core. The comforting heat lingers long after bathing, promoting deep relaxation and offering respite from the stresses of daily life. It is highly recommended for individuals desiring an authentic balneotherapy experience in Japan's northern frontier.

The Yubatake source, naturally gushing from Kusatsu Onsen's iconic Yubatake (Kusatsu's central hot-water field), holds a distinguished history. During the Edo period, it was ranked as the highest-ranking Ozeki in the Onsen Banzuke, recognized alongside the Shirahata source as one of Kusatsu's two major hot springs. Its powerful, pH2 water, permeated with a sulfurous aroma, imparts a refreshing, tightening sensation upon the skin. A soak in this historic, renowned hot spring cleanses the body and mind, offering deep relaxation and rejuvenation from daily fatigue. It is a must-visit for those seeking to feel the energy of a historic hot spring and desire a complete refresh.

The Yubatake source, naturally gushing from Kusatsu Onsen's iconic Yubatake (Kusatsu's central hot-water field), holds a distinguished history. During the Edo period, it was ranked as the highest-ranking Ozeki in the Onsen Banzuke, recognized alongside the Shirahata source as one of Kusatsu's two major hot springs. Its powerful, pH2 water, permeated with a sulfurous aroma, imparts a refreshing, tightening sensation upon the skin. A soak in this historic, renowned hot spring cleanses the body and mind, offering deep relaxation and rejuvenation from daily fatigue. It is a must-visit for those seeking to feel the energy of a historic hot spring and desire a complete refresh.

The Mandaiko source, originating from traces of past mining development, is deeply intertwined with Kusatsu Onsen's unique yumomi culture and its long history of toji (therapeutic bathing). Its highly acidic waters, among Japan's most potent, deliver a distinctive tingling sensation, awakening both mind and body and offering a sense of rejuvenation. The high-temperature blessings penetrate deep into the core, leaving you with a surprisingly light and refreshed feeling after your bath. We invite those seeking a genuine toji experience, a true escape from daily life to restore their mind and body, to discover the profound power of this spring.

This is one of the most well-known sources in Noboribetsu, a leading onsen destination in Hokkaido. It continuously flows at a high temperature of 96.5°C, embodying the raw power of the earth. The highly acidic water, with a pH of 2.2, provides a tingling sensation on the skin and a refreshing feeling after bathing. Its rich iron and sulfate content offers a powerful bathing experience that feels as if it's awakening both mind and body. It's a spring for those who wish to reset from daily fatigue, gain new vitality, and feel nature's energy throughout their entire being.

Esan Onsen Ryokan sits in Kashiwano, Hakodate, at the foot of the active volcano Mt. Esan, and keeps the air of a traditional healing inn. It is said to have begun when an earlier generation gathered the springs they found into a hand-dug basin, and today the naturally flowing source still pours from a single inlet into wooden tubs and over their edges. The water is nearly clear with a faint yellow-green tinge, a scent of iron and a sharp acidity, and white deposits form around the inlet. It is a strongly acidic sulfate spring rare in Hokkaido, and because the water is lukewarm the inn closes in winter.

The Yubatake source, naturally gushing from Kusatsu Onsen's iconic Yubatake (Kusatsu's central hot-water field), holds a distinguished history. During the Edo period, it was ranked as the highest-ranking Ozeki in the Onsen Banzuke, recognized alongside the Shirahata source as one of Kusatsu's two major hot springs. Its powerful, pH2 water, permeated with a sulfurous aroma, imparts a refreshing, tightening sensation upon the skin. A soak in this historic, renowned hot spring cleanses the body and mind, offering deep relaxation and rejuvenation from daily fatigue. It is a must-visit for those seeking to feel the energy of a historic hot spring and desire a complete refresh.

The Yubatake source, naturally gushing from Kusatsu Onsen's iconic Yubatake (Kusatsu's central hot-water field), holds a distinguished history. During the Edo period, it was ranked as the highest-ranking Ozeki in the Onsen Banzuke, recognized alongside the Shirahata source as one of Kusatsu's two major hot springs. Its powerful, pH2 water, permeated with a sulfurous aroma, imparts a refreshing, tightening sensation upon the skin. A soak in this historic, renowned hot spring cleanses the body and mind, offering deep relaxation and rejuvenation from daily fatigue. It is a must-visit for those seeking to feel the energy of a historic hot spring and desire a complete refresh.

Shirahatage Genzen, located in Kusatsu Onsen and adjacent to Yubatake (Kusatsu's central hot-water field), is said to have been discovered by Minamoto no Yoritomo. Historically, it served as the stage for 'Jikan-yu' (timed bathing), supporting balneotherapy culture, and is truly considered the soul of Kusatsu. Its distinctive aroma and powerful waters, which feel as though they firm the skin, seem to awaken the mind and body from within. Surrendering to its embrace offers a pure moment to shed daily clamor and rediscover one's true self. This spring is a sanctuary for those seeking a fresh start and rejuvenation.

The Yubatake source, naturally gushing from Kusatsu Onsen's iconic Yubatake (Kusatsu's central hot-water field), holds a distinguished history. During the Edo period, it was ranked as the highest-ranking Ozeki in the Onsen Banzuke, recognized alongside the Shirahata source as one of Kusatsu's two major hot springs. Its powerful, pH2 water, permeated with a sulfurous aroma, imparts a refreshing, tightening sensation upon the skin. A soak in this historic, renowned hot spring cleanses the body and mind, offering deep relaxation and rejuvenation from daily fatigue. It is a must-visit for those seeking to feel the energy of a historic hot spring and desire a complete refresh.

Originating from the fumaroles of Owakudani, born from the eruption of Hakone volcano approximately 3,000 years ago, this artificially developed hot spring began to be supplied to Sengokuhara and Gora by Hakone Onsen Kyokyu Co., Ltd. in Showa 5 (1930). Its renowned milky white waters, blended with naturally gushing spring water, offer a pleasant sensation that tightens the skin and a powerful restorative warmth that penetrates deep into the body's core. After bathing, you'll feel surprisingly refreshed and light. It's a perfect companion when you seek to feel the Earth's energy and achieve deep relaxation and rejuvenation for your mind and body.

The Mandaiko source, originating from traces of past mining development, is deeply intertwined with Kusatsu Onsen's unique yumomi culture and its long history of toji (therapeutic bathing). Its highly acidic waters, among Japan's most potent, deliver a distinctive tingling sensation, awakening both mind and body and offering a sense of rejuvenation. The high-temperature blessings penetrate deep into the core, leaving you with a surprisingly light and refreshed feeling after your bath. We invite those seeking a genuine toji experience, a true escape from daily life to restore their mind and body, to discover the profound power of this spring.