Turn the pages of I-IN, a new Japanese architecture book

view of minimalist interior at cartier guest lounge in tokyo by I-IN

I-IN's Cartier lounge in Tokyo

(Image credit: Tomooki Kengaku)

published 26 April 2025

I-IN is a spatial studio that exemplifies Japanese design at its finest, its growing portfolio spanning from sleek sci-fi offices to the luxe minimalism of a Cartier lounge – and the firm has now distilled its creativity into a newly published tome on its work for all to soak up. The book, fittingly, simply titled I-IN and with a thoughtful essay by Wallpaper’s own Singapore editor Daven Wu, has just been released, offering a heady mix of minimalist architecture and Japanese heritage.

Turning the pages in I-IN's new book

The Tokyo-based architecture studio, headed by founding partners Yohei Terui and Hiromu Yuyama since its inception in 2018, has been involved in a slew of projects – large and small, but all tackled with the same attention to detail and refreshing, pared-down approach. Its portfolio includes the headquarters for Japanese haircare brand Kinujo, a lushly restrained Cartier Guest Lounge, and the futuristic office of Warp Studio – all in the Japanese capital.

I-IN Tokyo designed Kinujo office — The I-IN-designed Kinujo office

The book from Frame Publishers presents all these and more, in a series of case studies that showcases the practice's elegant balance of innovation and simplicity, tapping into Japan's traditions and design heritage, while infusing it with 21st-century sensibility.

Still, I-IN's minimalism is not that of cold reduction – far from it, the firm's spaces feel warm and welcoming, soft and malleable, tactile and approachable. Its expert use of curves, textures and materials speaks to that, making up an architectural environment that feels meaningful and fit for purpose.

Wu writes in his eloquent introduction of one of the practice's biggest strengths: 'Many architects and designers settle for a signature look very early in the game. Or, at the very least, they strive for one – a visual DNA that semaphores the world precisely, which is the creative mind behind a particular design. It's a useful calling card, especially as it helps the studio stand out from the pack for its distinctive house style.

warp studio japanese office with white walls, glass widows and a brown sofa with black table — Warp Studio interior

'For I-IN and its founders Hiromu Yuyama and Yohei Terui, no obviously distinctive markers in their work might lead the observer to instantly say of a built space, “Ah yes, that's work by I-IN. It's unmistakable.”’ It is the studio's “quiet thoughtfulness”, design clarity and flexible approach that shine through in every commission, making this emerging architecture duo a calm force to be reckoned with.’

warp studio japanese office meeting room — Warm tones at Warp Studio

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Ellie Stathaki is the Architecture & Environment Director at Wallpaper*. She trained as an architect at the Aristotle University of Thessaloniki in Greece and studied architectural history at the Bartlett in London. Now an established journalist, she has been a member of the Wallpaper* team since 2006, visiting buildings across the globe and interviewing leading architects such as Tadao Ando and Rem Koolhaas. Ellie has also taken part in judging panels, moderated events, curated shows and contributed in books, such as The Contemporary House (Thames & Hudson, 2018), Glenn Sestig Architecture Diary (2020) and House London (2022).