Hoshino Resorts has opened its first Yamagata property in Zao Onsen. The 49-room ryokan combines a fourteen-sided tower with communal spring baths, regional craft and a rooftop wellness area.
Kai Zao opened in Yamagata’s Zao Onsen on 15 October 2026, bringing a 49-room ryokan to one of Tohoku’s established mountain destinations. The opening is Hoshino Resorts’ first in Yamagata Prefecture. Its fourteen-sided tower, designed around views in different directions, gives the hotel an immediately recognisable form, while the experience inside draws on the hot spring water and local craftsmanship that already distinguish the area.
The building’s geometry has practical consequences for the rooms. The regular polygon creates trapezoidal spaces, and the aspect changes with their position and height. Furniture from Yamagata makers, including Tendo Mokko, sits alongside paper lighting incorporating safflower petals. Safflower, historically traded as a valuable dye, supplies the red tones used throughout the interiors. For guests choosing a room, the direction of the windows is therefore worth considering alongside the category and floor area.
Bathing takes place in several quite different settings. In the communal bathhouse, Kai has arranged three pools around the strength of Zao’s acidic sulphur spring. The sequence begins with plain hot water, continues through a diluted bath and reaches a pool supplied with undiluted source water. The hotel calls them the zero, fifty and hundred baths, although it notes that the middle pool’s concentration varies with the water added for temperature control. The names describe the bathing arrangement rather than three separate natural springs.
That distinction extends to private bathing. Selected rooms have open-air baths, but the hotel specifies that these use plain hot water. Travellers who particularly want an in-room onsen should check that detail before booking. The communal spring water is the main attraction for those interested in Zao’s distinctive bathing tradition; a private tub offers a different experience. Treating every bath in a hot spring hotel as interchangeable would miss an important part of what is being offered.
Higher in the tower, a separate wellness area combines a sauna, cold bath and places to sit between sessions. A route through the upper spaces leads to the rooftop garden and jet bath, whose shape refers to Okama, the crater lake associated with the Zao mountains. The arrangement gives visitors a reason to move through the building and spend time looking out across the surrounding landscape. It also means the hotel has substantial shared facilities for guests whose holiday does not revolve around skiing.
The food takes another route into Yamagata. Dinner is served as a regional kaiseki meal drawing on the ideas of shojin cooking, with mountain ingredients and safflower references in the presentation. The announced main course is a hotpot combining duck, mushrooms and seri, the Japanese herb often translated as water dropwort. Despite the influence of Buddhist vegetarian cooking, this is not a vegetarian menu. Anyone with dietary requirements should make arrangements directly rather than infer them from the description.
A quieter activity continues the safflower theme. The hotel offers a year-round session in which guests put impressions from their journey into a short poem, using the Japanese five-seven-five pattern. It is listed as free and does not require a reservation. Alongside the lounge and bathing areas, it provides something to do at the hotel without booking another excursion.
The project is the third investment of the tourism revitalisation fund jointly operated by Hoshino Resorts and RISA Partners, following Kai Okuhida and Kai Akiu. RISA’s opening announcement describes an ambition to attract stays throughout the year. That fits the facilities, but a newly opened hotel cannot yet demonstrate a settled pattern of seasonal demand. For visitors, the immediate point is simpler: Zao has gained a new accommodation option that puts bathing and time indoors at the centre of the stay.
Reaching it still requires a mountain transfer. The hotel gives an approximate forty-minute journey from JR Yamagata Station by taxi or local bus, after the rail trip from Tokyo, and lists no hotel shuttle. Its winter driving guidance recommends suitable tyres or chains. Allowing time for that final leg makes more sense than planning around the Shinkansen arrival alone. Guests can then leave room for the baths and dinner on their first evening, rather than arriving with an itinerary that has already used up the day.