Tsukubasan Onsen (筑波山温泉)

Introduction: The Sacred Peak of the Twin Gods and the “Toro-toro” Waters of pH 10.3

Majestically overlooking the Kanto Plain at an elevation of 300 meters, Tsukubasan Onsen (筑波山温泉) is an intellectual and spiritual gateway defined by Japan’s “Creation Myth.” Centered around the 3,000-year-old Tsukubasan Shrine, this destination honors the deities Izanagi and Izanami, the progenitors of the Japanese islands.[1, 2] Geologically, the area is a marvel of “Deep Saponification”; its primary source, Sogami-no-yu, wells up through ancient gabbro rock formations to reach a staggering $pH$ 10.3—one of the highest alkaline levels in Japan. For the international traveler, Tsukubasan offers a profound encounter with “Mountain Mysticism.” It is a place to soak in “Liquid Silk” while watching the lights of Tokyo glow on the horizon, explore the legendary “Toad Stone” of Gama-no-Abura folklore, and experience the elite hospitality of a region where the spiritual energy of the peaks meets the precision of a global science city.

Key Information Table

The Healing Waters: The “Alkaline Mirror” of the Gods

The water at Tsukubasan Onsen is geologically unique due to its interaction with the mountain’s Gabbro (筑波石) core. Classified as a Strongly Alkaline Simple Spring, its $pH$ value ranges between **10.18 and 10.3**.
The Saponification Mechanism: In balneology, a $pH$ over 10 functions as a powerful natural soap. The water reacts with the skin’s triglycerides to emulsify oils and soften dead keratin, leaving the skin feeling “Toro-toro” (viscous) in the bath and exceptionally smooth after drying—the definitive “Bihada-no-yu” (Spring of Beauty).[9, 5]
The “Sky Bath” Effect: Most hotels feature “Tenku” (Sky) tubs. At facilities like Hotel Aokiya or Tsukubasan Keisei Hotel, you can soak in these silk waters while gazing at the “Sea of Clouds” ($Unkai$) or a panorama that stretches to Mt. Fuji and the Tokyo Skytree on clear days.[10, 5]

Top 5 Recommended Stays

• Tsukubasan Onsen Edoya (筑波山江戸屋): Address: 728 Tsukuba. Established 370 years ago, this is the region’s historic anchor. It features a private “Spring Garden” and a footbath. It is the premier choice for travelers seeking Edo-period dignity combined with modern comfort.[6, 7]
• Tsukubasan Hotel Aokiya (青木屋): Famous for its 180-degree panoramic rooftop bath. It offers the most spectacular night views of the Kanto plain.
• Tsukubasan Keisei Hotel: Located at the highest point of the resort (542m altitude), offering “Tenku-no-yu” (Baths of the Heavens). Ideal for hikers who want immediate access to the ropeway.[4, 11]
• Tsukuba Onsen Hotel: Address: 395 Tsukuba. Known for its high concentration of the original “Sogami” source water and its unpretentious, traditional atmosphere.[6, 12]
• Hotel Ichibo (一望): A modern facility that collaborates with the “Tsukuba-no-yu” day-spa, known for its extensive private chartered baths—perfect for families and couples.

Must-Visit Neighborhood Spots: Toad Stones and Fortune Rocks

Gama-ishi (Toad Rock): The legendary site where the samurai *Nagai Hyosuke* reportedly conceived the “Gama-no-Abura” (Toad Oil) ointment sales pitch. It is a major power spot for fortune and business success.
Tsukubasan Shrine: A vast sanctuary covering the entire mountain. Visit the main hall to witness the “Gojinbashi” bridge, a gift from Shogun Tokugawa Iemitsu.
Daiseki-kasane: Located at 750m elevation; place a small stone with a wish here to have it reach the mountain deities.
Tsukuba Space Center (Nearby): For a contrast in “Creation,” visit the JAXA facility in the lower city to see full-scale rockets and satellite technology.

Local Gastronomy: The Kingdom of “Fukure” Oranges and Medicinal Soba

Food in Tsukubasan is defined by the “Fukure Mikan” (Lucky Oranges), a tiny, aromatic citrus variety grown on the mountain slopes.[13]
Fukure Soba: Buckwheat noodles topped with grated orange zest for an invigorating aroma.
Hitachi-Aki Soba: High-grade buckwheat known for its deep nuttiness.
Vegetarian/Vegan Survival:
Koushiki Sabou (香色茶坊): Located 10-mins away in central Tsukuba, this is a strictly Vegan & Halal restaurant. They offer “Medicinal Curry” and plant-based bento boxes using organic root vegetables.
Ritz’n (りっつん): A macrobiotic hub serving brown rice sets and 100% plant-based Japanese desserts near the mountain base.[6, 14]

Cultural & Historical Context: The Progenitor of the East

The spirit of Tsukuba is inseparable from the 国産み (Kuni-umi) legend. Historically, the mountain was a site of “Kagakutai”—ancient festivals where men and women met to exchange poetry and find partners. Today, the Tsukubasan Plum Festival (Feb–Mar) and the Momiji Matsuri (Nov) continue to weave these ancient social and spiritual rhythms into the modern calendar.

Practical Travel Tips for International Visitors

• Tattoo Policy: Tsukuba-no-yu and Hotel Ichibo allow entry if tattoos can be covered by a waterproof sticker ($10cm times 15cm$, available at the front desk). For larger tattoos, we recommend booking Private/Kashikiri baths at Aokiya or Edoya.[15, 8]
• Connectivity: Wi-Fi is high-speed and standard in major ryokan lobbies. Mobile signal is reliable even near the summit peaks.
• Cash & Payments: While major hotels accept all credit cards, the Tsukubasan Shuttle bus and small shrine-stalls are strictly cash-only (JPY).
• Language Barrier: Staff at Edoya and Yoshikawaya have significant experience with international guests. English menus are standard at vegan hubs like Ritz’n.[14]

2025-2026 Latest Updates

In February 2026, the 53rd Tsukubasan Plum Festival (Feb 7 – Mar 15) will feature 1,000 blooming trees against the massive “筑波石” rocks. On January 1, 2026, the cable car will operate from 4:30 AM for the “Hatsu-hinode” (First Sunrise), with a record number of slots for foreign residents.

Safety & Manners

In the alkaline water, the floors are **exceptionally slippery**—walk with care. Because the mountain is a designated “National Park Preservation Zone,” do not remove any rocks or plants. Respect the silence of the shrine’s “Sanpai” zones; Tsukubasan is a place where prayer and nature are one.