Yokokawa Onsen (横川温泉)

Introduction: The 1,000-Year “Four-Day Water” and the Alkaline Purity of the Satomi Valley

Tucked away in the quiet, pastoral landscape of the Satomi district in northern Hitachiota, lies Yokokawa Onsen (横川温泉). This destination—a small, intimate spa hub centered around three historic inns—is defined by its extraordinary geological potency and its role as a “Hidden Satoyama Sanctuary”.[1, 2] Legend states that the spring was discovered in 1057 by the legendary samurai commander Minamoto no Yoshiie (Hachiman Taro) during the Zenkunen War; after soaking his battle wounds, they were miraculously healed in just four days, leading to its ancient name, “Yodachi-no-yu” (The Four-Day Water).[3, 4] Boasting a staggering $pH$ 10.1, Yokokawa is a scientific marvel of “Natural Saponification.” For the international traveler, Yokokawa offers a profound encounter with Balneological Purity. It is a place to soak in “Liquid Velvet” that acts as a natural serum, explore the dramatic heights of the Ryujin Suspension Bridge, and experience the warm, unpretentious hospitality of a region where the history of the Abukuma mountains meets the sweetness of Hitachi Aki Soba.[5, 6]

Key Information Table

The Healing Waters: The Science of pH 10.1 “Velvet”

The water at Yokokawa Onsen is geologically prized for its extreme alkalinity, one of the highest levels recorded in Ibaraki Prefecture. Classified as an Alkaline Simple Sulfur Spring, it emerges as a cold mineral spring ($12.9$-$16^circ C$) and is experts-heated to $42^circ C$.
The Saponification Logic: With a $pH$ of 10.1, the water acts as a “Natural Soap.” It reacts with skin oils to create a slight “slippery” or “viscous” sensation in the tub, effectively emulsifying sebum and dissolving dead keratin cells—leaving the skin feeling remarkably smooth, earning it the title “Bijin-no-yu” (Beautiful Woman’s Water).[5, 10]
The Sulfur Synergy: The trace amounts of sulfur stimulate peripheral circulation and metabolic repair, which historically supported the rapid tissue healing reported in the Yoshiie legends.
The flagship facility, Yamadaya Ryokan, features a dramatic two-story high open-ceiling bath area that looks directly out onto the mountain stream and small waterfalls, providing a multisensory nature therapy.[10, 15]

Top 3 Recommended Stays

• Yokokawa Onsen Motoyu Yamadaya Ryokan (元湯 山田屋旅館): Address: 1409 Orihashi-cho. Founded in 1753 (Horeki 3), this inn is the historic guardian of the spring.[4, 15] It is famous for its **”Okukuji Kaiseki”** cuisine featuring charcoal-grilled mountain trout and Inoshishi-nabe (Wild Boar Hotpot). It is the premier choice for luxury travelers seeking deep history.[5, 10]
• Nakano-ya Ryokan (中野屋旅館): Address: 1404 Orihashi-cho. A 200-year-old inn that has evolved into a modern wellness hub.[3, 16] It features a **Barrel Sauna** (low-temp bedrock bath) and even has a Ground Golf course. It is Wi-Fi equipped throughout and offers private family baths—perfect for digital nomads and families.[3, 17]
• Tomoe-ya Ryokan (巴屋旅館): Address: 1408 Orihashi-cho. The most homey and cost-effective of the three. It maintains an authentic “Toji” (Healing) atmosphere with a focus on simple, high-quality mineral soaking and budget-friendly stay plans.[9, 13]

Must-Visit Neighborhood Spots: Bungee Jumps and Blue Bridges

Ryujin Large Suspension Bridge: A 40-minute drive away. One of Japan’s longest pedestrian bridges at 375 meters. In March 2025, it underwent a full repainting to a vivid “Ryujin Blue”.[18, 6]
Ryujin Bungee: Experience Japan’s largest bungee jump from a height of 100 meters above the emerald Ryujin lake.
Satomi Fureai-kan: A short drive away, offering hands-on workshops in Soba-making and Konjac-making using local mountain spring water.[19]
Eigen-ji (Momiji Temple): While in the district, visit this temple in nearby Daigo for spectacular autumn foliage in November.[20]

Local Gastronomy: The Scent of “Hitachi Aki Soba” and Wild Game

Food in Yokokawa is defined by the high mineral runoff of the Abukuma mountains and the rich traditions of the Satomi forests.
Hitachi Aki Soba: Widely regarded as Japan’s highest-quality buckwheat. It is served fresh at all three ryokans, often as part of a multi-course “Okukuji Kaiseki”.[5]
Okukuji Shamo (Gamecock): Muscular, flavorful poultry raised for over 100 days . Try the “Shamo Sukiyaki” at Nakano-ya.
Vegetarian/Vegan Survival:
Cafe & Space Connect (常陸太田): A 20-minute drive, this cafe offers **gluten-free sweets** and vegetable-forward menus using soy milk cream .
Vegan Cafe terra (Mito Transit): If arriving via Mito, this is the region’s premier strictly vegan hub for “Neo-Vegetarian” lunches .
Satoyama Kaiseki: At Yamada-ya, specify “Vegetarian” at least 3 days in advance; they can provide an all-mountain vegetable feast—ensure you specify “Katsuo-dashi nuki” (No fish stock).[10]

Cultural & Historical Context: The Spirit of Hachiman Taro

The spirit of Yokokawa is anchored in the year 1057. Minamoto no Yoshiie’s presence turned this valley into a “Place of Resilience.” Historically, it served as a vital recovery base for soldiers and foresters moving through the Hitachi highlands. The fact that these inns have remained in operation for 200-300 years reflects a community dedicated to preserving the “Natural Mirror” of their waters for future generations.

Practical Travel Tips for International Visitors

• Tattoo Policy: Yokokawa is welcoming. Nakano-ya offers a **Barrier-Free Private Family Bath** (2,000 JPY / 60 min) that is 100% tattoo-friendly.[21, 22] Small tattoos are generally ignored in the public baths of the other inns.
• Connectivity: Nakano-ya has excellent Wi-Fi in guest rooms. In the valley, mobile signal is stable for all major carriers.
• Cash & Payments: While Nakano-ya and Yamada-ya accept major credit cards and **PayPay**, Tomoe-ya is strictly cash-only (JPY) .
• Access: The bus from Hitachiota Station to “Orihashi-Jumonji” departs 4-5 times a day. Major inns offer a Free Shuttle from the bus stop if booked in advance.[8, 5]

2025-2026 Latest Updates

In March 2025, the Ryujin Large Suspension Bridge painting project was completed, restoring its brilliant blue color for the 2026 season.[18, 6] In June 2025, the new Streamer Fieldpost Hitachiota Satomi cafe is scheduled to open, adding a modern design element to the historic onsen route .

Safety & Manners

In the 強アルカリ (Strongly Alkaline) waters, the tubs are **exceptionally slippery**—always use the handrails.[9] Because these are small inns, **walk softly in the wooden corridors** to respect other guests’ rest. If driving from Tokyo in winter (Dec–Feb), ensure your car has Winter Tires for the mountain passes around Satomi.[23] Finally, respect the quiet of the Satomi valley; Yokokawa is a place where the sound of the Tenryu River is the primary entertainment.[11]