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KAI by Hoshino Resorts hotels
Hot-spring inns tell regional stories through craft, seasonal kaiseki dinners and the water itself.
KAI makes each hot-spring stay an introduction to a Japanese region, with local craft in the rooms, seasonal kaiseki dinners, and cultural experiences tied to the town or landscape. Launched by Hoshino Resorts in 2011, the collection ranges from small villa retreats to larger ryokan, with the water and traditions of each place shaping the visit.
9 KAI by Hoshino Resorts hotels in 1 country on the Luxury Hotels Atlas, each placed on the six LHA Tiers.
- Owned by Hoshino Resorts
- Worldwide: 24 properties, all in Japan
- On the atlas: 1 High Luxury, 5 Core Luxury, 1 Accessible Luxury, 2 Near Luxury
History
The Hoshino family’s hot-spring hospitality began in Karuizawa in 1914, long before KAI became a separate brand in 2011. The Aso villas joined that new family from an earlier incarnation. Later ryokan took their subjects from places such as Hakone, Beppu, Yufuin, and Lake Poroto, with local water, craft, and culture giving each stay its identity.
Timeline
- 1914 — The Hoshino family opens Hoshino Onsen Ryokan in Karuizawa, Nagano. That inn is the root of the company that later creates KAI.
- 2006 — Twelve villas open in June in the Aso caldera under the name KAI ASO, each with an outdoor hot-spring bath.
- 2011 — KAI launches as the onsen ryokan brand. In October the caldera villas take the name used today, KAI Aso.
- 2018 — KAI Sengokuhara opens in Hakone in July: 16 rooms, a private terrace bath in each, and art made by artists who stayed before the debut.
- 2021 — KAI Beppu, designed by Kengo Kuma, has its grand opening on July 8 on Beppu Bay.
- 2022 — KAI Poroto opens on January 14 at Lake Poroto, the first KAI in Hokkaido, designed by Hiroshi Nakamura. KAI Yufuin, Kuma's rice-terrace ryokan, opens on August 3 as the 20th KAI. KAI Unzen opens on November 25 beside the Unzen Jigoku steam field, the 22nd KAI and the first in Nagasaki.
- 2024 — KAI Nikko closes on March 1 for a long renovation. KAI Akiu opens on April 25 in Miyagi, then counted as the 23rd KAI. KAI Kawaji ends operations on September 30. KAI Okuhida opens on September 5 in Hirayu, the first KAI in Gifu. KAI Hakone closes on September 1 for renovation.
- 2025 — KAI Hakone reopens on August 13 with a Tokaido Road theme. KAI Matsumoto closes on September 1 for a full rebuild.
- 2026 — The brand marks its 15th year and sets an aim of 30 ryokans by 2030. KAI Kusatsu opens on June 7. KAI Miyajima opens on July 23, the first KAI in Hiroshima. KAI Matsumoto reopens on August 4. KAI Zao is scheduled for October 15. KAI Aso is due to close at the end of October.
The houses to know
- KAI Sengokuhara, Hakone, Japan — A 16-room atelier ryokan where every terrace has a private bath and the walls hold art made in residence.
- KAI Poroto, Shiraoi, Japan — Hiroshi Nakamura's lake ryokan, with a cone-shaped bathhouse on the Ainu shore of Lake Poroto.
- KAI Beppu, Beppu, Japan — Kengo Kuma's bay ryokan, a larger onsen-town house where every room looks at the water.
- KAI Yufuin, Yufu, Japan — Kengo Kuma's rice-terrace ryokan, 45 rooms and villas under Mount Yufu.
- Hoshino Resorts KAI Unzen, Unzen, Japan — Fifty-one rooms beside the Unzen Jigoku steam, with Nagasaki's Japanese, Chinese, and Dutch mix in the rooms.
- Hoshino Resorts KAI Kirishima, Kirishima, Japan — Forty-nine rooms on the Takachiho slope, every one looking at Sakurajima.
- Hoshino Resorts KAI Okuhida, Hirayu Onsen, Japan — A Hida-timber ryokan of 49 rooms, 28 of them with a terrace spring, under the Northern Alps.
- Hoshino Resorts KAI Matsumoto, Matsumoto, Japan — A 2026 rebuild in Asama Onsen: 29 music suites, record players, and the brand's first Italian dinner.
- KAI Akiu, Akiu Onsen, Japan — A 2024 river ryokan in Sendai's old spring valley, themed around Date Masamune and the Natori.
Newest openings
- KAI Kusatsu, Kusatsu Onsen, Gunma, Japan, opened June 7, 2026. Ninety-four rooms sit on a quiet hill under Mount Kusatsu-Shirane, linked to the famous hot-spring town by a guest tunnel. Silk Art Rooms use Kiryu weaving, and the baths draw two acidic sources, Bandaiko and the milder Nishinogawara. Tatsuro Sasaki Architects led the basic design. A soba restaurant, Soba Kappo SAI, is the first KAI dining room open to day visitors.
- KAI Miyajima, Miyajimaguchi, Hiroshima, Japan, opened July 23, 2026. Fifty-four rooms, all called Umigiri (Sea Mist) Rooms, look across the water toward Itsukushima Shrine. Thirty have private open-air baths. KOO Architects shaped the house. An infinity bath faces the Seto Inland Sea, and an ishiburo stone sauna revives a Kamakura-period warming room that had nearly vanished from this coast. It is the first KAI in Hiroshima.
- Hoshino Resorts KAI Okuhida, Hirayu Onsen, Japan, opened September 5, 2024, at the edge of this window. Forty-nine rooms, 28 of them with outdoor hot-spring baths, sit near the Northern Alps. Sakakura Building Research Institute designed the buildings, and Kanade Design Office did the landscape of alleys, footbaths, and a courtyard. Hida bentwood, Hida-shunkei lacquer, and Hida dyeing fill the rooms. It was the first KAI in Gifu.
Opening next
- KAI Zao, Zao Onsen, Yamagata, Japan, is scheduled to open on October 15, 2026. Forty-nine Crimson Modern Rooms take their color from Yamagata safflower. Shuhei Kamiya and Kamiya Architects led the design. The stay is a walk upward through acidic baths and saunas to a rooftop terrace and jacuzzi inspired by the Okama crater lake. Reservations opened on April 22, 2026. The property already appears on the brand list of 24.
- KAI Ureshino, Ureshino Onsen, Saga, Japan, is scheduled for summer 2027. It will be the first KAI in Saga, built around a spring long famous for the skin. A room count is still unpublished.
- Hoshino Resorts aims to reach 30 KAI ryokans by 2030, each introducing a different onsen culture. No further named sites beyond Zao and Ureshino were confirmed in the sources reviewed through April 2026.
Every KAI by Hoshino Resorts hotel on the atlas
Japan
- KAI Sengokuhara — Hakone · High Luxury
- Hoshino Resorts KAI Kirishima — Kirishima · Core Luxury
- Hoshino Resorts KAI Unzen — Unzen · Core Luxury
- KAI Beppu — Beppu · Core Luxury
- KAI Poroto — Shiraoi · Core Luxury
- KAI Yufuin — Yufu · Core Luxury
- Hoshino Resorts KAI Okuhida — Hirayu Onsen · Accessible Luxury
- Hoshino Resorts KAI Matsumoto — Matsumoto · Near Luxury
- KAI Akiu — Akiu Onsen · Near Luxury
Open The Maison in the atlas for KAI by Hoshino Resorts's full dossier, with prices and maps.