SOAN KOSUMOSU

Yufuin Onsen has about 700 source wells, and this inn has its private source without exception.
In addition, all hot springs in the inn are free-flowing hot spring water.
The spring quality is a Weak Alkaline Simple hot springs with pH (hydrogen ion concentration) of 8.2.
Simple hot springs means a hot spring with less than 1,000 mg of dissolved substances per kilogram of spring water. Despite the word "simple", it is a very deep hot spring.
Since human skin is generally weakly acidic (pH 4.5 to 6.0), soaking in an alkaline hot spring will dissolve dead skin cells on the surface of the skin and make it smooth and silky. Because the dead skin cells are removed, the skin will feel as if it has been reborn after soaking in the hot spring. Due to this effect, the (weak) alkaline character of the hot spring water is said to be "Hot spring for beautiful skin".

Sodium ions (112 mg) and Hydrogen carbonate ions (191 mg) are nearly half of the dissolved substances. These combine to form baking soda. The main ingredient in commercial bath additives that claim to have skin beautifying effects is often sodium bicarbonate, or baking soda, so the hot springs here can truly be called a cleansing natural bath additive.
In general, the active ingredients in commercially sold bath additives are usually concentrated at 50-150 mg/kg, but the dissolved substance in this hot spring is 645 mg, so a comparison shows that it is 4 to 12 times more concentrated.
Baking soda (sodium bicarbonate)stimulates blood circulation and its emulsifying action washes away skin fats and secretions like soap.
Although the content of baking soda (sodium bicarbonate) does not appear in the name of the spring, combined with its weakly alkaline component, it is a valuable hot spring that can be expected to have a W-cleansing effect on the skin. This skin beautifying effect can be felt immediately after bathing, but it is said to be felt again three weeks to one month later, when the skin's metabolism has gone through a full cycle.

It also contains 192 mg of metasilicic acid, which is nearly 4 times the standard value (50 mg/kg). Metasilicic acid is a natural moisturizing ingredient used in some cosmetics. It is "Hot spring for beautiful skin", which leads to moist skin after the bath. Not only cleansing but also moisturizing, it is a very luxurious hot spring.
However, be cautious because even hot spring for beautiful skin can have its pitfalls. The cleansing effect may cause the skin to dry out easily after the bath. For those with dry skin, or in winter when the air tends to be dry, it is recommended to apply moisturizing cream after bathing.

In 2014, the "Guidelines for Mineral Spring Analysis Method" were revised, and for the first time, indications unique to simple hot springs were defined. The indications for this type of hot spring are Autonomic instability, Insomnia, and Depression. These are all indications related to mental health, which may be due to the fact that simple hot springs have a relaxing effect that is superior to other hot springs because this spring is low irritating and gentle. It is also used for stroke rehabilitation and is sometimes called "Hot spring for stroke" or "Hot spring for neuralgia". It is also called "Family hot spring" because it is gentle enough for people of all ages and both sexes to enjoy.

Among the hot spring resorts in Yufuin, which have a reputation as a hot spring area of longing, the "Soan Kosumosu" is now regarded by experts as one of the "Top three" ryokans of Yufuin. Although located in the center of the hot spring area, the inn maintains a quiet atmosphere due to its location on a side street off Yunotsubo Kaido, which is lined with souvenir shops and other stores.
The private hot spring water with its own source of hot spring for beautiful skin can be experienced in the popular detached house with an open-air bath or in a private open-air bath for private use.
In 2017, the inn underwent a major renovation, mainly in guest rooms, by inviting Eiji Mitooka, the charismatic designer who gave birth to JR Kyushu's luxury sleeper train, the "Cruise Train Nanatsuboshi in Kyushu".
The inn has become very popular because guests can stay in a design space equivalent to the "Natsunoshi" train, which is said to cost around 1 million yen depending on the boarding plan, for the price of an overnight stay at a ryokan. Guests can see the craftsmanship and design of Japanese craftsmen everywhere in the inn.
Did you know that the cuisine at Yufuin's hot spring inns is said to be so highly regarded that it is said to compete for first or second place in Japan? The reason for this is actually attributed to the fact that the inn's first head chef established the "Yufuin Ryori Kenkyukai" (Yufuin Cooking Study Association) in 1998 with only chefs and not the inn's management. The association regularly exchanged information on recipes and presented new dishes to improve each other's culinary skills. The chefs who have followed this tradition have served as the inn's successive chefs, so one can naturally imagine the level of cuisine at "Soan Kosumosu".
This inn is typical of the small, high-class ryokan that can only be found in Yufuin. As well as the alkaline simple hot spring water, which is gentle on the skin, the hospitality of the entire staff extends to everyone, from children to the elderly, and guests are sure to have a pleasant time.
Travel Journal