Masutomi Onsen: Day-Use Hot Spring Baths & Prices

Rising along a ravine that leads up toward Mount Mizugaki in the mountains of Hokuto City, Masutomi Onsen is a spa known for water rich in radium. Its distinctive reddish-brown water has long been enjoyed in the classic cure style, sinking in slowly for a long, unhurried soak in the mild, lukewarm bath. It is also spoken of as one of the secret baths of Takeda Shingen, said to have been discovered while mining for gold.

Highlights

Clear mountain streams run around the hot spring area, framing a quiet backcountry landscape. The spa also sits near the trailheads for the celebrated peaks of Mizugaki and Kinpu, making it an easy base for anyone wanting to immerse themselves in nature. Savoring the low-temperature, lukewarm source over a long, unhurried soak is the way of this spa, and the mood of an old-time cure resort still lingers strongly here.

Enjoying the Seasons

Early summer wrapped in fresh green and the autumn foliage that dyes the ravine red and gold are especially lovely and draw many visitors. Summer stays cool as a retreat from the heat, while winter offers stillness ideal for focusing on the cure. The scenery around Lake Mizugaki is beautiful year round, offering a pleasant stop on a drive or a walk.

Access and Basic Information

The spa lies at the end of a mountain road toward Mount Mizugaki from the Sudama interchange on the Chuo Expressway by car. By public transport, access is by bus from stations such as Nirasaki on the JR Chuo Main Line, and services are limited, so checking timetables is essential. The source is on the mild side and known as a radium spring of the carbon-dioxide and sodium type, a water well suited to long soaking. Note that the area's main day-use facility can change its operating status due to renovation and the like, so if day-use bathing is your aim, confirm the opening status before you go.

Practical Travel Notes

• Since the style is a long, unhurried soak in mild water, allow ample time for your stay.
• Day-use operation can change with renovation or season, so always confirm the opening status before visiting.
• Close to the Mizugaki and Kinpu trailheads, it pairs well with climbing or hiking.
• With few buses, it is important to note the outbound and return times in advance when using public transport.
• In the mountains the mornings and evenings turn chilly, so a layer is welcome even in summer.

A Quick Tip

The way of this spa is to settle in for a long soak in the mild water, so you can enjoy lingering without overheating. The surroundings are rich in mountain nature, so pairing your visit with hiking or a walk makes it all the more rewarding. As the day-use facility is sometimes closed, plan your stay or drop-in after checking the latest operating information to be sure.

Practical Information for Your Visit

• Day-use bathing: Masutomi Onsen "Furokaku, the Inn with a Natural Rock Bath" (6672 Obi, Sutama-cho, Hokuto City / TEL 0551-45-0311) / between 12:30 and 14:00, up to 1 hour per visit / 1,000 yen per person (indoor bath only) / closed every Tuesday and on the inn's own closing days
• Private-room rest plan: 10:00-15:00 or 12:30-17:30 / 3,500 yen per person (1,000 yen for each additional hour, up to 2 hours extra). Within your allotted time you may use the indoor bath and the rock bath as many times as you like. A private reserved bath costs an extra 2,000 yen per hour per use
• Facility currently closed: The Hokuto City day-use hot spring "Masutomi no Yu" (6438 Hishi, Sutama-cho, Hokuto City) has been closed since April 2023 for the time being, for facility inspections and other work
• Spring quality: Known for its lukewarm radium-bearing source water, with a tradition of toji (therapeutic bathing) in which you soak for long periods in sources of differing temperatures. For the reputed benefits, please check the hot spring analysis certificate posted at each facility
• Access: About 30 minutes from the Sutama IC on the Chuo Expressway via the Masutomi Radium Line / about 60 minutes from Nirasaki Station on the JR Chuo Main Line by Yamanashi Kotsu Town Coach bus bound for "Masutomi Onsen", getting off at the terminus (1,230 yen). The seasonal "Kayagatake Mizugaki Denen Bus" on the Mizugaki route also takes about 60 minutes (1,340 yen)
• What needs to be reserved: Day-use bathing at Furokaku (telephone reservations accepted from 3 days in advance; those with a telephone reservation have priority), the private-room rest plan (must be reserved between 3 days and 1 day before your visit), and the private reserved bath
• Bathing etiquette: At Furokaku the indoor bath is cleaned from 11:00 to 12:30 every day and cannot be used then. The rock bath alternates between men and women by time slot
• Safety notes: As this is a mountainous area, mornings and evenings are chilly even in summer. In winter, be prepared for icy roads and snow

* Buses are infrequent. Be sure to check the times for both your outward and return journeys in advance.

(Sources: Furokaku official website, Hokuto City Tourism Association official website and others. As of July 2026)