Zenshichi no Yu, also called Ohira Hotel on its Japanese site, is an inn in Zao Onsen, Yamagata City. It owns two hot-spring sources that flow on their own from caves on the grounds, and it says every bath is 100 percent source water, milky white and strongly acidic, with no added water, no heating and no recirculation. Before you book, three things matter: the mixed open-air bath requires bathing wear and is women-only from 15:00 to 18:00; winter stays have much earlier cancellation fees; and the buildings have no elevator, with some wings lacking air conditioning.
Zenshichi no Yu at a glance
| Item | Official information |
|---|---|
| Address | 825 Zao Onsen, Yamagata City, Yamagata |
| Hot springs | Two private sources, strongly acidic, 100% free-flowing |
| Baths | 10 in all: 7 private, 2 indoor, 1 garden bath (mixed, bathing wear) |
| Check-in / out | 15:00 / 10:00 (last check-in 18:00 on dinner plans) |
| Meals | Dinner from 18:00, breakfast from 7:30 |
| Prices | From 10,500 yen per person, tax included (room only, five adults sharing) |
| Extra charges | Bathing tax 150 yen; heating fee 350 yen (Dec 1–Mar 31) per adult |
| Pets | Pet rooms kept separate from standard rooms |
| Phone | +81-23-694-9422 (8:00–20:00) |
From the official site and booking pages, read October 15, 2026.
The inn tells the story of Zao Onsen’s discovery around the year 110 and says its waters have flowed for 1,900 years. It describes its open-air bath as the first built in Zao Onsen and the town’s only mixed open-air bath. The whole inn is non-smoking.
The ten baths at Zenshichi no Yu
Which baths are there?
| Bath | How it works |
|---|---|
| 7 private baths | Booked from 10:00 to 21:00; after 21:00, free use with a door plate |
| 2 indoor source baths | Men and women swap by time; closed 30 minutes from 18:00 for cleaning |
| 1 garden open-air bath | Mixed, bathing wear required; women only 15:00–18:00 |
From the official bath page and Japanese booking page, read October 15, 2026.
The two sources are named Tsujiya and Ohira. The inn’s history page gives a pH of 1.25 to 1.6 for Zao Onsen’s strongly acidic water.
How do the private baths work?
For outside visitors, the private baths cost 1,000 to 7,500 yen depending on the season and the bath. The stay plans on the booking page are marked private baths free; book a slot between 10:00 and 21:00, or use them freely after 21:00 by turning the plate. A private sauna, Bishamonten, costs 5,000 yen for staying guests for 90 minutes, for one to four people. Our private bath fees guide compares how other inns charge.
What should I know about the acidic water?
The inn asks guests to take off jewelry and accessories before bathing; the water is strongly acidic.
Can I bathe with a tattoo?
None of the official pages, in Japanese or English, mention tattoos. Ask the inn before you book; our tattoo and onsen guide explains what to ask.
Rooms at Zenshichi no Yu
Which room types are there?
Standard rooms and pet rooms are completely separate. The special room Unkai sits on the 4th floor of the main building, 42.3 square meters for two to five guests, with two king-size beds and free drinks in the fridge; the inn notes there is no elevator. The north wing has Japanese-style rooms of 16.2 to 19 square meters with a washlet toilet; they have no air conditioning, only fans. The west wing has Western-style rooms of 17.3 square meters that take three guests with an extra bed, and the main building has two large Japanese-style rooms for small groups of up to about ten.
Can I bring a pet?
Yes, in the pet rooms, which include the special room Juhyo, opened in January 2024. A pet-only private bath, Hotaru no Yu, costs 2,700 yen for 75 minutes, by reservation.
Meals at Zenshichi no Yu
What are dinner and breakfast like?
Dinner starts at 18:00 in the dining area and breakfast at 7:30; breakfast is a set Japanese meal or a buffet, depending on the number of guests. Plans offer Yamagata beef or Yonezawa beef. The signature dish is the Tsujiya pot, an aluminum pan modeled on Zao’s Okama crater at 1/50,000 scale: you grill on the “slopes” and cook shabu-shabu in the “crater.” Rice comes from contract farms in Miyagi and Yamagata, and vegetables from a garden run by the young proprietress.
Can the inn handle allergies or a special diet?
The FAQ asks you to give details of allergies when you book, and says the kitchen will do what it can. The official pages say nothing about vegetarian or halal meals.
Prices, children, cancellation and payment at Zenshichi no Yu
How much does a stay cost?
The Japanese booking page lists prices per person, tax included, and they fall as more people share a room. The room-only plan starts at 10,500 yen with five adults in one room; breakfast plans start at 11,500 yen, the standard Yamagata beef plan at 14,500 yen, the Yonezawa beef plan at 16,500 yen, and the special room Juhyo at 39,000 yen. On top, Yamagata City charges a bathing tax of 150 yen per adult per night (see our onsen bathing tax guide), and from December 1 to March 31 the inn adds a heating fee of 350 yen per adult. The city also plans an accommodation tax of 3 percent of the room charge from April 1, 2027, according to the Ministry of Internal Affairs.
What do children cost?
On the room-only plan, a child with bedding costs 3,300 yen and a child without bedding 2,200 yen. Other plans show their own child rates on the booking page. The inn has yukata in two children’s sizes.
What is the cancellation policy?
For stays from December to March, the Japanese booking page lists free cancellation up to 150 days before, then 20 percent from 120 days, 30 percent from 90 days, 50 percent from 60 days and 100 percent from 30 days before. For other months, the inn’s FAQ and booking pages give different free-cancellation days, so confirm the rule with the inn when you book. See our hotel cancellation guide.
How do I pay?
The FAQ says most credit cards are accepted, though not on every plan. If you prepay online, the booking page notes the contract is with Time Design Co., Ltd., the booking engine’s travel agency.
Getting to Zenshichi no Yu in Zao Onsen
How do I get there by train and bus?
The access page gives about 2 hours 30 minutes on the Yamagata Shinkansen to Yamagata Station, then about 40 minutes on the Yamagata Kotsu bus to Zao Onsen. From the bus stop it is about 15 minutes on foot, or call the inn and its bus will pick you up within the Zao Onsen area.
Is there a shuttle from Yamagata Station?
The official pages differ on this, so ask the inn before you plan around one.
Can I drive in winter?
Parking is free in three lots. In winter the inn asks drivers to use studless tires and lends chains free of charge.
What foreign guests should know before staying at Zenshichi no Yu
- Pack for the stairs: the inn has no elevator.
- If you need air conditioning in summer, avoid the north wing rooms, which have fans only.
- On dinner plans, arrive by 18:00.
- The mixed open-air bath is bathing wear only, and women-only from 15:00 to 18:00.
- The inn’s name appears in more than one English spelling, so note the phone number: +81-23-694-9422.
Frequently asked questions
Do I need a swimsuit for the mixed open-air bath at Zenshichi no Yu?
Can I bathe with a tattoo at Zenshichi no Yu?
What time is check-in at Zenshichi no Yu?
What is the winter cancellation policy at Zenshichi no Yu?
Can I bring my dog to Zenshichi no Yu?
Bottom line (2026): Zenshichi no Yu is a Zao Onsen inn built around its own two acidic hot-spring sources, with seven private baths, a mixed open-air bath in bathing wear, and rooms for guests with pets. Arrive by 18:00 on dinner plans, check the winter cancellation dates, and confirm transport and any tattoo questions with the inn.
Sources
Every fact on this page is from Zenshichi no Yu’s official pages: home (Japanese), English page, baths, hot-spring history, rooms, meals, access, FAQ, the official booking page (Japanese) and the official English booking page; Yamagata City’s bathing tax page; and the Ministry of Internal Affairs’ notice on the Yamagata City accommodation tax. All were read on October 15, 2026. Prices and rules change; check the official site before you book.
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