“We’re sensitive about everything from every angle. Otaku mentality is very Japanese,” says 51-year-old Katayama. “And it’s about craftsmanship. Craftsmanship is not only creating to fulfil other people, but also creating to fulfil yourself.”

Even if his name doesn’t ring a bell, you have probably been inside a space designed by him. They include fast-fashion chain Uniqlo’s flagship stores in Paris, London, New York, Berlin, Shanghai, and Tokyo, and one-offs such as Nike’s Air Max installation at the Tokyo National Museum in March 2017. He is the go-to interior designer for Japan’s fashion industry.

In the past few years alone, Katayama has designed stores in Tokyo for fashion labels Verbal and Yoon’s Ambush, and for United Arrows in the city’s Roppongi Hills. He designed French patisserie Pierre Hermé’s Tokyo store, and redesigned it last year.

Why street style is over, in the eyes of one of its original stars, and the menswear trends he’s seeing in Hong Kong and Japan

Katayama’s first foray into designing stores for the fashion industry came 20 years ago, when he designed the groundbreaking store for cult street wear designer Nigo’s line A Bathing Ape. Five books have been written about his vision for retail spaces, and he has worked with fashion labels such as Thom Browne, Diesel, and A.P.C.

So how did a self-confessed “bad student” from Okayama in southwestern Japan end up designing international spaces for fashion’s biggest names?

“I was in high school when I first encountered fashion,” Katayama says. “In Japan, Comme des Garcons and Yohji Yamamoto were huge at the time. They gave me a big culture shock. It was so natural for me to see fashion as a new culture and it really hit me hard.”

His father owned a furniture shop, and Katayama began toying with the idea of being a designer. “I entered school in Osaka, where I studied interior design. I realised then there was such a job as designing fashion boutiques, which were so hip in Japan. Everything crossed over and I thought it was my fate to go into design.”

In spring 2017, Katayama held an exhibition in Tokyo called “The Encyclopedia of Masamichi Katayama: Life is hard … Let’s go shopping.” The playful title belied the breadth and depth of the pieces on display, taken from Katayama’s personal archive of objects he “shopped” for over the years.

From cactuses to taxidermy, and works by American pop artist KAWS to mid-century modern furniture, the collection is testament to Katayama’s love for retail.

“I’m a big fan of design, fashion, and culture. I’m a designer but I’m a consumer, too – my consumer side might be a little bit bigger than my designer side,” he says. That allows Katayama to create a retail environment that immediately engages and envelops the shopper.

One element of his success is his ability to insert elements of conceptual art into mainstream consumerist culture.

“My work is like a translator. We have to tell the story of each brand, let them envision the life with the product,” he says. Because design doesn’t use words as a medium, how can new people be initiated into a brand’s universe without words?

For Katayama, creating an air of familiarity is important. “One of the approaches I use is people’s subconscious mind. If you see a design and you feel you might have seen it in some other place or in some other form, it clicks in the subconscious. You start to wonder why this place is so intriguing – so you will enter.”

Another approach he takes is the Instagram effect. “We have to engage the social media world – how the design will be photographed and spread through social networks.”

How Nautica’s David Chu gave up retirement and created a hugely popular Beijing event space

Katayama is on a mission to spread the gospel of design. As well as managing Wonderwall, he teaches design as a professor at Musashino Art University in Tokyo. This year he will be working on Japan House, a cultural centre occupying three floors of an art deco building in London which will showcase the best of Japanese art, design, gastronomy and technology.

Recent falls in sales at retail stores aren’t lost on Katayama. “Web shops are invading our industry, but it’s natural because convenience wins,” he says.

He has always been a step ahead – from building futuristic spaces in the late 1990s to pioneering experiential brand extensions by offering, say, a cafe experience for a car brand. So what are his thoughts on the future of retailing?

“I don’t know if my interior design future is brighter or darker. But it’s definitely becoming more interesting. What we’re doing is to provide experience – and maybe we’re going backwards, going analogue to give more ‘primitive’ experiences.

“As the internet evolves towards convenience, I think my industry is evolving towards ‘inconvenience’ – the joy you receive from a time-consuming experience.

“For example, in 10 years, if you want to go from one point to another, you won’t need a driver, you’ll just need a vehicle to take you. If you want to have the joy of the ride, then you will drive yourself. So it’s a different joy. My job is to create the less inconvenient to be even more joyful.”