A designer sauna co-developed by Maruni Woodwork, ONE SAUNA, and Wataru Kumano, featuring furniture-grade craftsmanship and IoT safety systems.

Where can I experience it?

Available from summer 2026 at 'COCO VILLA Kyoto Rurikei' and 'Aquaignis Bettei Yu-no-Yama Sosuikyo'.

Yoshino hinoki from Nara Prefecture, known for its soft texture and balanced thermal properties.

Equipped with an IoT system that automatically shuts off heaters and alerts staff upon emergency button press.

Can I book in advance?

Yes, via the official websites of the respective accommodations when booking your stay.

Maruni Woodwork × ONE SAUNA Co-Developed Designer Sauna 'kupu sauna' to Be World's First Installed at Two Accommodation Facilities

Published Jun 16, 2026 6:30 PM ・ Updated Jun 16, 2026 9:56 AM ・ 13 min read ・ Source: PR TIMES

The designer sauna 'kupu sauna,' co-developed by Maruni Woodwork and sauna brand ONE SAUNA with product designer Wataru Kumano, will be introduced at two Japanese accommodation facilities—the world's first such deployment. A fusion of furniture-grade craftsmanship and thermal experience design will offer premium sauna experiences starting summer 2026.

Maruni Woodwork Co., Ltd. (Hiroshima City, Hiroshima Prefecture; President & CEO: Hiroshi Yamanaka) and Libertyship Co., Ltd. (Miyazaki City, Miyazaki Prefecture; CEO: Haruya Agematsu, operator of sauna brand 'ONE SAUNA') have jointly developed the designer sauna 'kupu sauna,' which will be introduced for the first time in the world at two accommodation facilities: 'COCO VILLA Kyoto Rurikei' (Nantan City, Kyoto Prefecture) and 'Aquaignis Bettei Yu-no-Yama Sosuikyo' (Komono Town, Mie Prefecture). This 'designer sauna,' combining furniture-grade finishing precision, ONE SAUNA's thermal and sensory design, and the design expertise of product designer Wataru Kumano, will now be offered as a real guest experience.

Key Points of This Release

・ The 'designer sauna' born from the collaboration of renowned furniture maker Maruni Woodwork, product designer Wataru Kumano, and domestic sauna brand ONE SAUNA will debut globally at accommodation facilities.

・ Two distinct facilities will feature the sauna: 'COCO VILLA Kyoto Rurikei,' a riverside standalone villa, and 'Aquaignis Bettei Yu-no-Yama Sosuikyo,' a detached ryokan with 100% natural hot spring flow.

・ ONE SAUNA received the Good Design Award in 2020. Upholding the philosophy of local production for local consumption, it uses Yoshino hinoki from Nara Prefecture.

・ Equipped with ONE SAUNA's proprietary IoT sauna management system (patented: Patent No. 7510172), it ensures comfort, energy efficiency, and safety through automatic pre-heating, automatic heater shutoff linked to emergency buttons, and automatic calls to administrators.

About kupu sauna

Founded in Hiroshima in 1928, Maruni Woodwork has championed the concept of 'industrializing craft,' creating products beloved by architects and designers worldwide. To apply its furniture manufacturing expertise to the extreme environment of saunas—exposed to heat and steam—product designer Wataru Kumano (principal of design office kumano) and ONE SAUNA, with its expertise in thermal and sensory sauna design, joined forces.

The resulting 'kupu sauna' achieves both furniture-grade finishing precision and the functional and aesthetic beauty envisioned by a product designer. Its signature half-dome curved structure allows steam generated during löyly to circulate along the dome's inner curves, softly descending onto bathers' backs for a one-of-a-kind sensory experience.

talk about kupu sauna

https://onesauna.jp/maruni-sauna/blogs/media/4320216142

The 'kupu sauna,' first unveiled at an event at Isetan Shinjuku in September 2025, is now being introduced into accommodation facilities and will be available for use.

Facility ①｜COCO VILLA Kyoto Rurikei (Nantan City, Kyoto Prefecture)

A newly built, standalone bungalow villa of approximately 91㎡ (plus a 61㎡ wooden deck), where the stream and seasons take center stage. Guests can enjoy the 'totonoi' (post-sauna well-being) experience while overlooking a flowing stream, using the Yoshino hinoki half-dome kupu sauna and a cold bath filled with natural spring water.

・ One kupu sauna unit installed in a scenic riverside location

・ Cold bath using natural water, with a complete circulation path including outdoor cooling

・ Entire villa rental space accommodating up to 10 guests (recommended for 6)

・ Scheduled to open around summer 2026

Facility ②｜Aquaignis Bettei Yu-no-Yama Sosuikyo (Komono Town, Mie Prefecture)

Guest rooms themed around natural materials:

'Kikoku (Time of Wood)' themed around wood

'Sekirou (Rocky Crags)' themed around stone

A secluded ryokan with 12 detached villas, offering 100% natural hot spring flow and premium cuisine. Each villa is designed around natural materials, and the 'Kikoku' and 'Sekirou' villas will feature the kupu sauna to harmonize with their unique atmospheres.

▼ 'Kikoku (Time of Wood)' – Wood-Themed Villa

・ Seamless flow from the villa to the sauna via a wooden deck

・ Equipped with Maruni Woodwork's 'totonoi chair' (kupu sauna chair)

▼ 'Sekirou (Rocky Crags)' – Stone-Themed Villa

・ Features a stone cold bath, enabling a full-cycle routine: sauna → stone cold bath → outdoor cooling

・ Equipped with Maruni Woodwork's 'totonoi chair' (kupu sauna chair)

ONE SAUNA / Local Sourcing in Sauna Construction

ONE SAUNA operates under the concept of 'local sourcing for saunas,' operating sauna facilities across six locations in Japan using regionally sourced wood. For this kupu sauna, 'Yoshino hinoki from Nara' is used. The soft texture and balanced thermal properties of Yoshino hinoki are maximized through furniture-quality finishing.

※ ONE SAUNA received the Good Design Award in 2020.

IoT Sauna Management System (Patent No. 7510172)

The kupu sauna is equipped with ONE SAUNA's patented proprietary IoT sauna management system.

・ Automatic pre-heating synchronized with reservation data optimizes operation time and enables energy-efficient management

・ Ensures optimal temperature is always ready upon guest check-in, delivering a premium customer experience

・ In case of emergency button press in the room, the heater is automatically shut off and administrators are automatically notified by phone—ensuring immediate response even in emergencies

This 'heat only what is needed, when it is needed' operation enables both high-quality guest experiences and sustainable operations for accommodation facilities.

Company Profiles

▼ Cocozaus Co., Ltd.

Facility Name: COCO VILLA Kyoto Rurikei

Address: 1-5 Kumino-ki, Oharuchi, Sonobe-cho, Nantan City, Kyoto Prefecture

URL: https://owners.coco-villa.jp/villa/kyotorurikei-22/

https://coco-villa.jp/

▼ Aquaignis Co., Ltd.

Facility Name: Aquaignis Bettei Yu-no-Yama Sosuikyo

Address: 4842-1 Komono, Komono-cho, Mie-gun, Mie Prefecture

URL: https://sosuikyo.com/

▼ Maruni Woodwork Co., Ltd.

Address: 24 Shirasuna, Yuki-cho, Saeki-ku, Hiroshima City, Hiroshima Prefecture

Founded: 1928

Representative: President & CEO Hiroshi Yamanaka

Business: Planning, manufacturing, and sales of furniture

URL: https://www.maruni.com/

▼ Libertyship Co., Ltd. (ONE SAUNA)

Address: 7275-1 Kaejita, Miyazaki City, Miyazaki Prefecture

Representative: CEO Haruya Agematsu

Business: Sauna development and operation, sauna facility production, provision of the IoT sauna management system 'ONE SAUNA'

Brand URL: https://onesauna.jp/

Corporate URL: https://libertyship.jp/

FACT BOX

Source: PR TIMES
Category: Partnership
Products / services: kupu sauna