Zenshichi-no-Yu

This inn is strongly impressed with its commitment to hot springs, even among Zao Onsen, which has a reputation for the quality of its springs. One of their passion for hot springs can be seen in the way of using the hot spring water. The baths are not circulated, filtered, or disinfected, but are always filled with fresh hot spring water, which is natural free-flowing hot spring water, and then overflowed to be replaced by new hot spring water. The temperature is adjusted by blending two different temperatures of hot spring sources, taking into account the temperature of the day , to create the right temperature. Guests can experience a "handmade" 100% free-flowing hot spring water.

It is also important to note that it is a private hot spring source. Hot spring water, like any other substance, begins to oxidize (deteriorate) when it comes into contact with the air. In other words, the shorter the distance from the source well to the bathhouse, the fresher the hot spring water. It is a great advantage to have the source well on the same site. Another advantage is that the spring source is naturally gushing, without the use of a motor to pump up the hot water. This means that the source is located close to the surface of the earth, and the hot spring water gushes out from there without the use of machinery to pump it up. Because of this, there is less chance of impurities being mixed in. This is a feature of Zao Onsen as a whole, but it is also a testament to the long history of this hot spring area, which dates back to a time when machines did not exist.
The amount of dissolved substances, which indicates the character of the hot spring, is extremely rich at 3,795 mg/kg, which is also one of the features of the hot spring.

The spring quality is "Acidic, Sulfur containing - Hydrogen - Sulfate springs". To put it simply, it is a hot spring that has three of the ten spring qualities that are currently classified: "Acidic springs", "Sulfur springs", and "Sulfate springs".

First, one of the conditions for "Acidic springs" is that 1 kg of hot spring water must contain at least 1 mg of hydrogen ions. The pH value (hydrogen ion concentration) of this hot spring is 1.5, which is acidic, and often shows strong acidity.
It is said to be "Hot spring for skin diseases" because it has very high antibacterial power and removes a wide range of causes of problems on the surface of the skin. Also effective against athlete's foot. And it is said to be good for sterilizing Staphylococcus aureus, one of the causes of Atopic dermatitis. This is because Staphylococcus aureus can be inhibited from reproducing in an acidic environment.
Other indications for spring quality include Plaque psoriasis, Impaired glucose tolerance (diabetes), and Epidermal suppuration. It is also said to be effective against Tinea (ringworm), Trichomonas vaginalis, and Scabies.

Next, as for "Sulfur springs", one of the conditions is that 1 kg of hot spring water contains 2 mg or more of total sulfur (the sum of (1) Hydrogen sulfide ions, (2) Thiosulfate ions, and (3) Free hydrogen sulfide). There are two types of Sulfur springs: Sulfur-type springs, which contain mainly (1) + (2), and Hydrogen sulfide-type springs, which contain more (3). Here at Zao Onsen, the water is a "Hydrogen sulfide-type Sulfur springs".
The spring water is milky white in color, and has many indications in common with "Acidic springs", including Atopic dermatitis, Plaque psoriasis, Chronic eczema, and Epidermal suppuration.
The Sulfur springs, like the Acidic springs, has a high antibacterial effect, so it is said to be "Hot spring for skin diseases" that is effective for all kinds of skin surface problems. In addition, sulfur springs remove excess sebum, making them ideal for people prone to acne and oily skin, and since they suppress the production of melanin, the substance that causes skin spots, it is also called "Hot spring for preventing skin spots" and can be expected to have a whitening effect as well. In other words, Sulfur springs is a typical "Hot spring for beautiful skin". The reducing effect of sulfur also reacts with active oxygen, a substance that causes aging, so a rejuvenating effect can be expected.
In addition, it is sometimes called "Hot spring for phlegm" because of its effectiveness in relieving asthma and improving the sharpness of phlegm.
One thing to keep in mind is that metal items such as rings and necklaces can discolor due to sulfur components, so remember to remove them when bathing.
Contraindications by spring quality for bathing include sensitive skin or mucous membranes, and dry skin in the elderly (*same as Acidic springs). In other words, "Sulfur springs", like "Acidic springs", are highly stimulating springs, so the sickly, elderly, and those with sensitive skin should be careful and are prone to "Hot spring fatigue". Many of the best hot springs are a combination of "Acidic" (antibacterial) and "Sulfur (hydrogen sulfide-type)" (skin-beautifying) springs. However, please keep in mind that the stronger the efficacy, the more stressful it is on the skin.

One of the conditions for "Sulfate springs" is that the main component of the anion is a sulfate ion. The indications for bathing by spring type are Cuts, Peripheral circulatory disturbance, Sensitivity to cold, Depression, and Dry skin.
The most important feature of "Sulfate springs" is that it promotes skin revitalization (activates metabolism). Therefore, it is effective for cuts, burns, acne, psoriasis, itching, chronic eczema, etc., and is sometimes referred to as "Hot spring for cuts".
The "Sulfate springs" is also highly effective for oily skin because of its ability to wash away excess oil from the skin. In addition, the sulfate ions have the effect of pumping more oxygen into the blood and rehydrating the skin, making it taut and moisturized, which is an anti-aging effect. This is why it is called "Hot spring for rejuvenation". It is also called "Hot spring for beautiful skin" in the same way as Sulfur springs.

The amount of "Metasilicic acid", a non-dissociated component besides cations and anions, should also be noted.
It contains 211.3 mg per kilogram of spring water, which is more than 4 times the standard value for hot springs (50 mg/kg). Metasilicic acid is used as an ingredient in some lotions and has moisturizing effects. Hot springs with high metasilicic acid content can be called "Hot spring for beautiful skin".

Lastly, as is well known among hot spring critics and other hot spring researchers, the spring quality of Kusatsu Onsen in Gunma Prefecture, a symbol of Japan's famous hot springs, and that of Zao Onsen are very similar, not to mention their pH values, and the types and balance of ions that make up the hot springs. Some even refer to Zao Onsen as the "Kusatsu Onsen of the North". However, it should be noted that Zao Onsen contains almost twice as much dissolved matter in 1 kg of hot spring water as Kusatsu Onsen.

Zao Onsen is a hot spring area located in the southeastern part of Yamagata City, Yamagata Prefecture, at the foot of the western side of the Zao Mountain Range, at an altitude of 900 meters. It is one of the best known hot spring areas in the Tohoku region of Japan, not only in terms of name recognition, but also in terms of the amount of hot spring water available.
The hot spring is said to have opened around 110 A.D., and is known as one of the oldest hot springs in Japan. Zao Onsen was called Mogami Takayu (now Zao Takayu) in ancient times, and was one of the three most popular hot springs in Ou Takayu ('taka' means 'high-up' and 'yu' means 'hot spring') along with Shirabu Takayu in the same prefecture and Shinobu Takayu in Fukushima Prefecture.
"Zenshichi-no-Yu” also has a long history, having been established in the middle of the Edo period (1603-1868), making it over 300 years old.
The inn's president, Zenshichi Okazaki, the 13th generation, has a deep knowledge of hot springs, which is reflected in the name of the inn, "Zenshichi-no-Yu". The president himself is constantly taking in new information and knowledge about hot springs and applying it to the inn he manages. When he is not on a business trip, he even holds a "Onsen Classroom" for guests who wish to attend after dinner.
The baths are also not to be missed. The number of private open-air baths has been increased to five, using an abundance of private hot springs. In addition, there are baths exclusively for pets and private saunas to enjoy. There is also the only mixed bathing open-air bath in Zao Onsen, although guests are required to wear bathing suits.
There are a total of 30 guest rooms, including 21 Japanese-style rooms, 3 Japanese/Western-style rooms, and 6 Western-style rooms, but there are also rooms that can accommodate with pets, special rooms with popular open-air baths, and more reasonably priced rooms.
Zao Onsen is popular in winter because of its proximity to ski resorts and its famous "Jyuhyo (tree ice)", but many people who mainly come for the hot springs seem to frequent the area regardless of the season.
In spring, there are many cherry blossom viewing spots, and in June, the area is crowded with cherry picking, followed by grape and peach picking in summer. In October, the autumn foliage season is in full swing.
The meals are not only delicious local rice, but also Yamagata beef, which is highly reputed, and other foods that are unique to Yamagata Prefecture, which is known as a treasure of food.
The inn is always attentive to the needs of its guests, and its desire to make them a reality as much as possible can be felt.
The staff's hospitality is natural, and they provide a comfortable environment. I was convinced that there are many repeat guests.