[KAI Kusatsu] Opening June 7, 2026. A guest-only tunnel connects a "serene inn" with a "lively hot spring town bustling with flowing water." The hot spring ryokan brand "KAI" proposes a new way to stay.

Hoshino Resorts' nationwide hot spring ryokan brand "KAI" will open "KAI Kusatsu" in Kusatsu Onsen, Gunma Prefecture, on June 7, 2026. The facility's concept is "A tunnel connecting a woodland hot spring inn and a hot spring town." Located on a hill at the foot of Mount Kusatsu-Shirane, its main feature is a guest-only tunnel that connects the "bustle of the hot spring town" with the "tranquil hot spring inn," proposing a new lodging experience. Guests can seamlessly move between two different worlds, enjoying the diverse attractions of Kusatsu's famous hot springs, Joshu's textile culture, and selectable kaiseki cuisine, offering a new stay style that touches the essence of Kusatsu Onsen.

Feature 1: Feel the "Serenity" at a hot spring inn surrounded by the nature of Mount Kusatsu-Shirane

A view of walking along a wooded path at "KAI Kusatsu," surrounded by trees.

Kusatsu Onsen has long been celebrated as "Kusatsu Senken Edo Gamae" and loved as a lively hot spring town (*1). Along the roads leading to the Yubatake (hot water field), which remains from the Edo period, many shops and inns line the streets. "KAI Kusatsu" is an extraordinary hot spring inn located on a quiet hill, set apart from the town's bustle. Inside, the design reflects the unique rock surfaces and vegetation of Mount Kusatsu-Shirane, created by the strongly acidic natural environment. As you walk along the wooded path, the gentle calls of wild birds echo, beautiful sunlight filters through the trees, and you feel the breeze. During your stay, you can wander among the buildings scattered throughout the garden, experiencing the rich natural beauty of Kusatsu and feeling the "healing of silence" firsthand.

*1: From the Kusatsu Town website

Feature 2: Two hot springs of the famous "Kusatsu" and the hot spring culture "Iroha" to savor history

A spacious indoor bath where you can enjoy two hot springs. An open-air bath surrounded by rich nature.

In the large public bath, two types of acidic springs with different characters are drawn to allow guests to feel the abundant blessings of Kusatsu Onsen, which boasts the largest natural outflow in Japan (*2). One is the "Bandai-ko Spring," characterized by the highest outflow volume, temperature, and strong acidity among Kusatsu's hot springs. The other is the rare and slightly milder acidic "Sai-no-Kawara Spring," which is drawn by a limited number of facilities. The indoor bath has three tubs, allowing guests to enjoy the different water qualities at varying temperatures, offering a "hot spring hopping" experience without leaving the inn. Additionally, staff conduct a "Hot Spring Culture Iroha" session to introduce the history and characteristics of Kusatsu Onsen, offering an experience that touches the essence of this famous hot spring.

■ Water Quality

Bandai-ko Spring: Acidic-hydrogen-chloride/sulfate spring

Sai-no-Kawara Spring: Acidic-aluminum-sulfate/chloride spring

■ Overview

Bandai-ko Spring: Hot bath (natural flow with added water), lukewarm bath, open-air bath

Sai-no-Kawara Spring: Lukewarm bath

*2: Kusatsu Onsen Portal Site

Feature 3: Fabric scenes designed by textile designer Reiko Sudo and a "Gotochi Raku" experience of Joshu craftsmanship

■ "Silk Art Room," a local room enveloped in art by a world-renowned textile designer

A guest room expressing Kusatsu's natural beauty with silk art. A guest room open-air bath overlooking the mountain range.

"KAI" offers local rooms that allow guests to immerse themselves in the region's culture. The local room at "KAI Kusatsu" is the "Silk Art Room," inspired by Gunma's history of thriving sericulture. The fabric decorations throughout the inn, including the guest rooms, are designed by internationally active textile designer Reiko Sudo. The main feature is the fabric wall art, which depicts the scene of Kusatsu with steam rising from the hot springs against a backdrop of majestic mountains, all in a single woven piece. The mountain range is expressed through the gradation of colors in the weave, and the steam is represented by finely cut silk threads. From a distance, it looks like a painting of Kusatsu's steam; up close, you can appreciate the delicate texture and three-dimensionality created by the silk threads. It is produced using the techniques of Kiryu, a textile-producing region. Lampshades made from silk threads and cocoons, cushions inspired by Kusatsu's alpine plants, and bed liners create a comfortable space.

■ "Joshu Zoguri: Spinning Silk," a local experience in a dedicated space to feel Gunma's textile culture

A local experience building reminiscent of the Tomioka Silk Mill. An experience of reeling thread from cocoons using a wooden hand-reeling machine.

As part of the KAI brand's hospitality, a "Gotochi Raku" (local experience) is offered to allow guests to experience the region's culture. In line with Gunma Prefecture, a textile-producing area that flourished with the silk industry of sericulture, silk reeling, and weaving, KAI Kusatsu offers "Joshu Zoguri: Spinning Silk." Following the handcraft tradition dating back to the Edo period, this is an authentic experience of reeling thread from cocoons using a wooden hand-reeling machine. The resulting thread can be made into a tassel as a souvenir. The local experience takes place in a dedicated building reminiscent of the Tomioka Silk Mill, which flourished as a model factory for machine silk reeling in modern times. By directly touching the delicacy and strength of the thread, the beautiful fabric decorations throughout the inn should become even more appealing.

■ "Fireplace Lounge" for relaxing time at your own pace

After bathing at KAI Kusatsu, we recommend spending time in the Fireplace Lounge next to the bathhouse. In the space surrounding the central fireplace, you can listen to the crackling sound of the fire and be enveloped in its pleasant warmth. Opening a book about the culture and nature of Gunma and Kusatsu while surrendering to the leisurely flow of time is also a pleasure.

A relaxing space around the fireplace.

Feature 4: Two dining options to choose from based on your stay style

Meals during your stay at KAI Kusatsu can be chosen from two types: the "Joshu Hoden Kaiseki," a KAI Japanese-style kaiseki, and the "Jigona Kikouchi Soba Kaiseki" enjoyed at the soba kaiseki restaurant SAI. Soba Kaiseki SAI is a restaurant located on the grounds of KAI Kusatsu and is the first KAI restaurant to be open for day-use guests. It also offers a la carte dishes and a wide variety of appetizers to enjoy before the soba, allowing for a different style of dinner from the kaiseki.

■ "Joshu Hoden Kaiseki" served in the dining area

Joshu Hoden Kaiseki. A semi-private dining room partitioned by fabric dividers.

In a semi-private dining room that maintains a sense of privacy, kaiseki cuisine that makes use of local food culture is served. The "Joshu Hoden Kaiseki" begins with an appetizer served in a vessel inspired by Kusatsu Onsen's Yubatake and Yumomi (stirring hot water), featuring dishes that fully bring out the rich culinary appeal of Gunma. The main dish is the "Joshu Joya Nabe" (nightly pot). The pot is served with a whole chicken thigh simmered in the broth. Enjoy Gunma's famous spinach and the tenderly simmered chicken thigh with the broth infused with chicken flavor. This is ideal for those who want to enjoy a leisurely meal.

■ Gourmet experience at "Soba Kaiseki SAI," also enjoyable for day visitors

Jigona Kikouchi Soba Kaiseki. "Soba Kaiseki SAI" standing by the banks of Sai-no-Kawara Park.

The stars of "Soba Kaiseki SAI" are the 100% buckwheat soba made with locally milled flour and a commitment to "kikouchi" (using only buckwheat flour and water), and a flavorful three-tier dipping broth made from bonito, kelp, and dried shiitake mushrooms. Located by the banks of Sai-no-Kawara Park, the restaurant's green, beautiful interior creates an open yet calm, adult atmosphere. Here, you can fully savor a gourmet experience centered on meticulously crafted soba. A wide selection of local sake, craft beer, and natural wine is also available, and the restaurant is open for "day-use" by non-guests.

Feature 5: Staff-recommended hot spring hopping and town walks unique to KAI

A walk through Kusatsu Onsen town. A stroll in Sai-no-Kawara Park.

Step through the guest-only tunnel, the main feature, and you are in the vibrant hot spring town.