Welcome to hell.
That's the catchphrase of Kannawa Onsen. Oita Prefecture's world-famous Beppu Onsen is officially known as the Beppu Eight Hot Springs and is made up of eight different hot spring resorts. Kannawa Onsen, one of these, has been spewing boiling water, hot mud, and steam for over 1,000 years. Until it was discovered in the Kamakura period, it was a place that humans could not approach, and was therefore called "Hell."
However, Jigoku no Yu is a rare and blessed hot spring. Rainwater that falls on the mountain seeps 300 meters underground, passes through a filter created by volcanic activity, and takes 50 years to spring up to the surface. This is only 16% of the rainwater.
"Hell Steaming," in which vegetables are steamed in one go using the intense steam from this hot spring, which reaches a whopping 99.6 degrees, is a specialty dish that has been around since the Edo period, when people began flocking to Kannawa Onsen.
Sally Garden's Touji Yanagiya Inn has a hot spring source on its premises, allowing guests to make their own hell steamed baths. The building, originally built in 1905, was taken over and renovated by the current proprietress, Eiko Hashimoto. Opened in 2014, the inn combines the styles of a traditional Japanese inn and a hot springs inn.
To ensure safety, the building has been restored from the ground up, but the glossy floorboards, beautifully designed fittings, corridors made of Nachi black stone, and the stone oven for Jigokumushi, the "Hell Cooker," remain intact in the cauldron in the courtyard. Guests are free to use it, and the steam from the hot spring comes out when you turn the tap. Because it is a private hot spring, the hot spring water, which oxidizes when exposed to air, remains exceptionally fresh here.
The hot spring water is drinkable, and when I tried it, I was surprised by its complex, deep flavor, rounded saltiness, and slight viscosity. During its 50-year journey, the hot spring water had combined with minerals and ions through chemical reactions with the geothermal heat, making it almost soup-like.
The proprietress, Eiko Hashimoto, gave us instructions on how to make Jigokumushi. The kamaba is also a salon where guests can gather and chat while waiting for the steaming to finish. 
You can prepare food by cutting vegetables in the kitchen. You can store ingredients you buy yourself in the refrigerator, and utensils and tableware are provided. 
Simply place the ingredients on a colander and cover the pot. In addition to vegetables, eggs, sausages, meat, seafood, and rice are also delicious. In the summer, I like to steam a whole corn and bite into it.
Cooking equipment and tableware are provided at the inn, and the steaming times for each ingredient are written down, so even beginners will have no problem. You can have the inn prepare a "steamed food set" for the essential vegetables in advance, but it's also fun to procure vegetables at a local store while browsing the selection.
At a supermarket in Oita that has a direct-from-the-farm section, I buy summer vegetables like eggplant, okra, cherry tomatoes, root vegetables like turnip, lotus root, and pumpkin. I cut up the amount of each vegetable I want to eat and arrange them on a colander, then put them in the Jigokugama pot and wait for about 12 minutes.
I was surprised when I tasted the steamed vegetables. The cherry tomatoes were almost sauce-like, the lotus root was particularly sticky, and the pumpkin was endlessly sweet. The eggplant was transformed into a fluffy, soufflé-like texture.
The flavor, which is a concentrated blend of each of the hot spring's characteristics, and the unknown potential that emerges are the result of Kannawa's unique hot spring ingredients and hot, strong steam.
From the Meiji to Showa eras, this building was a lodging where farmers and coal miners would stay for long periods to recover from illness or to pamper themselves during the off-season. Some people would bring ingredients from their local areas, so Jigoku steaming was likely both a source of nourishment and a source of enjoyment for them.
However, modern toji are diverse. They can be used for retreats, workcations, staycations, time alone, or time with family. Toji Yanagiya offers a variety of rooms to suit all types of stays, including a new wing with hotel functionality, a nest with a study, a detached building that can be rented as a whole, and the main building in the style of a toji inn.
The hot spring water flows directly from the hotel's own hot spring source. It is rich in metasilicic acid, a natural moisturizing ingredient, and has a weak acidity similar to that of skin and a weak salt content similar to that of bodily fluids, making it known as "Beppin no Yu." 
The photo shows the new wing (ryokan section), which has been renovated from Japanese-style rooms into a modern style. In addition to the simple main building (hot spring treatment section) which is suitable for long-term stays, the Nest, which comes with a study and mini-kitchen and is perfect for workcations, and two types of annex buildings perfect for families, there are a variety of accommodation options available. 
The space blends original details with antique furniture, and is harmoniously complemented by art pieces such as stencil dyeing and tile paintings by sculptor Michiharu Mochizuki.
You can also choose your meals however you like. For example, you can warm up your body with hell steaming on the first day, and then enjoy Italian food made with local ingredients at the attached restaurant on the second day. You can also stay overnight and use the nearby restaurants and bento shops.
"Rather than healing, Kannawa is a hot spring that restores vitality and makes you feel at peace. It discharges energy and then recharges that empty space."
Mr. Hashimoto said, "The steam has been entrusted to us by the gods." The steam of Kannawa has energized people throughout the ages. If you take a quick dip in the hot spring and exit quickly, your body will truly feel refreshed and light.
