Motoyu Onsen (元湯温泉)

Introduction: The Cradle of the 1,200-Year Heritage

Deep in a primeval forest on a quiet mountain, where the Akagawa River begins its journey, sits Motoyu Onsen (元湯温泉)—the “original” spring. Discovered in 806 AD by high priests, it was once a thriving settlement known as “Motoyu Sengen” (1,000 inns) before a catastrophic landslide in 1659 buried the town. Today, only three secluded lodges remain, offering a “once-in-a-lifetime” encounter with Japan’s most mysterious waters.

For the international explorer, Motoyu is the ultimate “Secret Hot Spring” destination. [20, 3] It is home to Japan’s only Ink Black Water and springs that change color from emerald green to milky white depending on the barometric pressure. [5, 10] Motoyu provides a meditative sanctuary that prioritizes spiritual recovery and a total immersion into the silence of the deep Tochigi mountains. [21, 3]

Key Information Table

The Healing Waters: The “Ink” and the “Jewel Box”

Motoyu’s thermal profile is scientifically unique due to its multi-source variety. Unlike most regions with a single water type, Motoyu offers three distinct mineral expressions: [24, 3]

• Sumi-no-yu (Ink Hot Spring): Located at Oidekan, this is the only spring in Japan containing a reaction between iron and hydrogen sulfide that creates a **jet-black** liquid. It is believed to warm the internal organs more deeply than any other water.
• Midori-no-yu (Green Hot Spring): An emerald green sulfur source that turns milky white as it oxidizes, effectively smoothing the skin with silica. [6, 10]
• Kajiwara-no-yu: A gentle salt spring named after a 12th-century warrior, prized for treating joint stiffness and exhaustion. [3, 25]

Top 3 Recommended Stays: The Guardians of the Source

• Hitou-no-yado Gensenkan (元泉館): Famous for its “Treasure Bath,” which has been visited for centuries by those seeking to treat infertility. It also features a rare **drinkable** source that aids in digestion. [13, 23]
• Oidekan (大出館): Perched on a cliff with mountain views. It is the sole provider of the legendary “Sumi-no-yu” and offers an authentic mixed-gender bathing culture with a respectful atmosphere.
• Ebisuya (ゑびすや): A traditional wooden ryokan that maintains a rustic, homey vibe. Known for its “Nursing Bath” atmosphere and historic connections to the samurai era. [26, 25]

Must-Visit neighborhood Spot: The 1659 Remnant

Motoyu Landslide Site: A sobering reminder of the 1659 Great Earthquake. The landscape surrounding the current inns shows the power of natural forces that reshaped the entire valley.

Local Gastronomy & Souvenirs

Heike Legacies: Breakfast at Ebisuya often includes **”Heike Natto”** (fermented soybeans) featuring the Taira clan crest.

Vegan & Vegetarian Options: Gensenkan provides vegetable-focused Kaiseki that highlights local **Shiobara Highland Daikon**. [27, 28] Consuming the drinkable spring water at the “Insen-jo” is also considered a vital part of the nutritional healing process here. [27, 29]

Practical Travel Tips for 2025-2026

• Tattoo Policy: Oidekan and Gensenkan are members of the “Secret Hot Springs Association” and are generally very welcoming to foreign travelers with tattoos. Discretion is key in mixed baths.
• Connectivity: This is a low-connectivity zone. Wi-Fi is available inside the inns, but mobile signal is non-existent in the gorge.
• 2026 Event: Motoyu will be a key stop for the **”Nasu-Shiobara Literary Walk”** (March 20–April 19, 2026), featuring a stamp rally and character panels from the game Bungo to Alchemist. [30, 31]

Safety & Manners

Winter Driving: Pickup service from the Shiobara BT is **highly recommended** even for confident drivers, as the final 5km road to Motoyu is narrow, steep, and prone to heavy ice. Bathing Manners: When entering the “Ink Bath,” be aware that the black residue will stick to your skin—rinse thoroughly with fresh water at the end to avoid staining your clothes or the inn’s towels.