“When I first arrived in Japan I didn’t really get a kick out of the food of flavours”, Rainer says. “It took some time getting used to the mellow flavouring and subtle seasoning.”

For a chef-turned-restaurateur who has become synonymous with Japanese cuisine the world over, I’m surprised by Rainer’s statement. He’s gone on to reach culinary fame for his global, Japanese-infused brands Zuma, Roka and Shochu Lounge, opening four izakaya-inspired restaurants in the UK and a further seven in cities such as Dubai and Istanbul—all with a mass cult following and in the space of just 12 years.

Rainer’s flagship restaurant Zuma, in London’s Knightsbridge, is where I met the impeccably dressed bon vivant (he hangs out with celebrities such as the famous motorsport star Felipe Massa in his spare time) on a warm day in June. Rainer is the picture of cool, dressed in a crisp white shirt, stone-coloured trousers and a leather jacket, having zipped through the city on his sleek black BMW scooter, which is now parked in front of the restaurant’s glass-fronted exterior. He is undeniably suave.

He’s also incredibly warm and approachable and before long we’re in full conversation about his love of two-wheeled modes of transport. “I would like a push bike,” he says, quickly adding: “But it’s not fast enough for me. I need speed.”

Speed is one word that has come to define Rainer and his culinary career in some ways over the last few years. For one, Zuma, Knightsbridge—which now has sister concepts in Hong Kong, Turkey, Dubai, Miami, Bangkok and Abu Dhabi—revolves around the traditional Japanese robata-style cuisine, which involves cooking food very quickly over a hot grill for maximum flavour. Then there is the fact of how swiftly Rainer’s concepts have climbed the ranks to culinary fame. Over the years, Rainer’s restaurants have become fine dining hotspots for ardent foodies and celebrity A-listers alike, including Jay-Z, Beyoncé and the Beckhams, who swoon over delicious morsels of sashimi and robata-grilled delicacies.

Conversely, I also get the feeling that whatever Rainer does, he’s not afraid to take his time and do it well and always out of respect for the Japanese culture which has lent itself to the super-successful restaurant concepts of his.

Although Rainer was born and grew up in Moselle Valley, a picturesque region in Germany, close to France, he doesn’t take much culinary inspiration from his childhood. Nor did his time spent in Munich or Cologne, where he worked as chef de cuisine in the Hyatt Regency, and his short stint in Australia, working as executive chef at the Park Hyatt Sydney, influence his later path. Rainer’s real culinary inspiration came from the six years he spent in Tokyo where he was head chef at the Park Hyatt Tokyo, responsible for the hotel’s six restaurants.

After leaving Japan, Rainer headed to the UK; full of ambition and the desire to open the Japanese-inspired restaurant he’d dreamt about throughout his time in Tokyo. It took a chance encounter with business mogul Arjun Waney to get Zuma off the ground in 2002. When Arjun and Rainer met, Arjun had been looking to open his first restaurant—more specifically, a Japanese restaurant—after he’d failed to get a table at London’s Nobu. “I was looking for someone who would invest in my idea and my hairdresser at the time said he knew this guy who wanted to open a restaurant, so he called up Arjun.”

Today, Rainer spends more time as a restaurant man than a chef. He’s extended his culinary empire across the globe and created a second brand—Roka—to meet the growing demand for the unique dining experience Rainer was offering at Zuma.

While Rainer’s first love is cooking (“my heart is still in the kitchen and I kind of miss it once in a while,” he adds), spending less time in the kitchen and more time looking after the business side of things has meant he’s been able to expand the Zuma brand to epic proportions.

In 2007, Rainer opened a Zuma in Hong Kong. A year later he launched Zuma Dubai and Istanbul as well as a further three Zuma restaurants between 2010 and 2014 to include Zuma Miami, Bangkok and Abu Dhabi. Rainer’s Roka concept has also grown considerably, with openings in London’s Canary Wharf and Mayfair and a Roka in Hong Kong (born at the same time as Zuma Dubai and Istanbul in 2008)—all slightly less formal than their big sister Zuma, but still with Rainer’s signature nod to the robata-style Japanese dishes.

“I could have opened more restaurants over the years but I didn’t feel the need. If I focus on one thing, then I do it right. That’s probably why we’ve opened relatively few restaurants since the launch of Zuma Knightsbridge,” he explains.

Rainer moved away from Japanese cuisine for the first time in over a decade last year, introducing Oblix on the 32nd floor of The Shard in London. Oblix’s menu references a New York grill, all infused with Rainer’s signature style of upscale, sophisticated, urban dining. “Originally I was approached to open a Zuma there but I said no.” He explains: “I’ve always said that I only want one Zuma in each city so that it keeps it special and unique to that location.”

Most recently Rainer opened a second Zuma in Turkey in the exquisite D-Hotel Maris, which is located where the Aegean and Mediterranean Seas meet, perched on the hillside of the Datca Peninsula. The restaurant is a seasonal pop up that went permanent after a successful first summer. “In every Zuma there is something that I love more than the others. In Hong Kong we have a spiral staircase. In Dubai we have two floors and a bar. In Miami, you sit on the river and watch the boats go up and down. In Istanbul you sit by the Bosphorus. If I had to say which one was my favourite, though, it would be this one [Zuma Knightsbridge], because I never expected it to come to this.”

Zuma does tradition meets laidback sophistication like no other. The Knightsbridge restaurant is the perfect example of Rainer’s unique culinary vision and style. “What I loved in Japan was the Japanese pubs called Izakaya. They are very similar to western pubs but the difference is that they are more food driven. You always have decent food in Japanese Izakayas. I wanted to capture the atmosphere of a traditional Izakaya but in a much more sophisticated way.

“The bar here,” he says, pointing to the lavish glass island that stands in the centre of Zuma Knightsbridge’s dining room, “breaks the ice and means that Zuma is not only a restaurant but a place where you can also have a good time. Izakayas are often not designed in any way—they are just a room with tables and benches, but I love design and I wanted a contemporary and timeless restaurant, along with the best food and the best service. But I didn’t want to lose the element of the Izakaya ethos, which is having a good time while eating and drinking. I think this is why Zuma has become so successful because you can dress up and feel good, or come in jeans and sneakers and also feel good.”

Zuma Knightsbridge is located exactly where I imagine a traditional Izakaya would be situated: in a side street just hidden away from the hustle and bustle of a main precinct, in this case the famous Brompton Road, home to Harrods and the city’s well-heeled crowd.

Zuma’s interior—put together by Tokyo-based architecture and design company Super Potato and headed up by designer Noriyoshi Muramatsu—is impeccably chic. What makes the design work so well with Rainer’s food philosophy is that both use few materials and don’t try to change the basic raw material. “It’s all about keeping things clean, using the best material and making sure it stays simple,” Rainer adds.

The setting might be glamorous, but Rainer’s food does the talking, especially the signature dishes that have remained on the restaurant’s menu since the restaurant opened. “We change dishes and develop new ones but not on a regular basis. That’s partly because a lot of these dishes are traditional and also because they are seasonal. Sixty per cent of the dishes are signature dishes and we don’t touch them.”

As we’re chatting, we are delivered two of Zuma’s signature dishes, ise ebi, whole native lobster tempura with spicy ponzu and Wagyu no sumibiyaki. We also sample a sashimi platter created by Zuma’s sushi master, Endo Kazutoshi. I’m blown away by the intricacy and dedication to authentic Japanese cuisine in each of the dishes, and fascinated as I watch them being prepared in the open kitchen and arrive at the table as and when they’re ready, intended for sharing.

Later this year Rainer will open another Roka in Aldwych, London, and his newest Zuma concept in New York. I’m curious to see if this culinary mega star ever has any doubts about opening more Zuma outposts. “London is the culinary epicentre of Europe… It’s the same with New York. It’s very competitive and there is always a fear that something could go wrong. But it’s that fear that stops you from being complacent,” he says. “And that competition is what keeps you on the edge.”

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