Julia Daniel, a 21-year-old university student from Texas, is determined to experience the best that Japan has to offer. She has already encountered Mickey Mouse in Tokyo Disneyland and travelled on the bullet train to the second city of Osaka. But the climax of her brief holiday takes place in a much less famous place — Uji, a quiet town in central Japan, where she joins a queue of other foreigners all here to satisfy the same craving.

When the doors of Nakamura Tokichi tea shop open, they hurry past the rest of the produce to a small display of metal tins. The shop rations them, putting only 40 on sale each day; within a few minutes, all have been sold.

Daniel comes away with three of the precious pots for ¥9,000 (£48) — three ounces of a fragrant green dust that people will travel across the world to buy.

It is matcha, the powdered green tea that is used in the Japanese tea ceremony. Until a few years ago, it was little consumed by anyone other than diners at the most traditional restaurants. But recently, and with increasing intensity in the past year, it has become an international craze.

“I’m obsessed with matcha,” says Daniel, who has dressed specially for the occasion in tea-like shades of green and brown. “It gives me energy, it has health benefits, and it’s way better than coffee. On Tik-Tok, Uji tea is a big trend, so I wasn’t going to miss this while I’m here.”

After securing her supplies of matcha, and eating a matcha-flavoured cake, she will visit the nearby Tea Museum and participate in the Matcha Grinding Experience. Uji is to matcha what the Champagne region is to sparkling wine, and the boom has brought a surge of business and visitors. But it is also a strain on a small and unglamorous local industry, thrust into international stardom in a way that seems to many to threaten the soul of matcha itself.

The traditional tea ceremony is an ancient meditative ritual that has more in common with a Christian Eucharist than brewing a quick cuppa. The powdered tea is mixed with hot water, stirred with a bamboo whisk into a thick bubbly concoction and drunk in a few sips from a ceramic bowl in a series of prescribed movements. The raw material also turns out to be a versatile ingredient that is now being used in ways that no Kyoto tea master would have imagined.

Matcha lattes, matchaccinos, matcha ice cream and matcha shakes are consumed from Sydney to Dubai. To a tea purist, the matcha recipe recommended by Daniel — matcha, oat milk, lavender syrup and ice — would be the equivalent of mixing a fine single malt with Irn Bru. But overseas demand for the tea has transformed the matcha market.

In 2023, matcha production was 4,176 tons, compared with 1,471 tons in 2010 — more than half is exported, much of it to the Middle East. It sounds like a commercial bonanza, but it is occurring in an industry ill adapted to the increased production necessary to cash in on the boom.

The consequence has been a green tea shortage that is driving up prices and frustrating customers and suppliers at home and abroad. If the Japanese industry does not rise to meet demand, the void will eventually be filled by cheaper Chinese products that will lower standards and expectations and break the monopoly of the high-quality Japanese original.

Making the finest matcha is a uniquely slow and fiddly process. It takes five years for a tea bush to mature after planting. At a certain stage in their growth, the leaves have to be shielded from the sun to preserve their flavour; the finest are harvested by hand.

The furnaces used to dry the leaves cost ¥100,000 (£530). They are ground in handmade granite mills that produce less than an ounce and a half each hour. Rising temperatures are making it harder to cultivate a plant that needs to grow slowly to preserve its sweetness and umami.

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Tea growers are ageing and shrinking in number; having grown the same product in the same way, sometimes for generations, they are slow to embrace change. “It’s like making a cricketer play baseball and expecting him to get it in a day or two,” says Shogo Nakamura, the seventh generation of his family to run the Nakamura Tokichi tea shop, which was founded in 1854.

Production could be increased by cutting corners and reducing standards of quality — the chances are that consumers of matcha smoothies would not notice if their tea was ground in mechanised mills rather than a stone pestle. But to many in Uji, this would be a tragic compromise for what may turn out to be a transient consumer boom.

Nakamura talks about the French concept of terroir — the combination of climate, soil and human practices and traditions that form the culture of a particular wine or cheese — and the need to apply that to matcha production. “Rather than a fashion, I’d call this a bubble,” he says. “The bubble will burst in the future. Our job is to tell the story behind this product and to keep making it in the right way. What we have now is lots of matcha buyers — we have to turn them into true matcha fans.”