TOKYO—Akio Takahashi remembers the boy who showed up to Meitoku Gijuku Junior and Senior High School on the island of Shikoku in southwestern Japan and trained differently and more rigorously than any of the hundreds of kids he coached. 

A young Hideki Matsuyama would wake up in his dorm room at 5 a.m. to run and hit balls before breakfast. He would shovel down his lunch so he could hit some more before heading back to class. While other students joked around on the course, Matsuyama was serious with every swing he took. 

“He practiced whenever he found time,” Takahashi says.

That paid off in a spectacular way at one course in particular: Kasumigaseki Country Club. It’s the course hosting these Olympics. It’s also the place that catapulted his career toward stardom, sending him on a path toward the historic major he would eventually win at the Masters. 

“In a way, Kasumigaseki has been a place and catalyst for me to progress and grow,” Matsuyama said. “So hopefully I could do the same this week and move on to another level.”

Matsuyama arrived in Japan to compete in the golf at these Olympics as the golden boy of Japanese golf. On Thursday, Matsuyama shot a 2 under 69, six shots behind first-round leader Sepp Straka of Austria. “If I say there’s no pressure I’ll be lying,” he said after the round. 

Hideki Matsuyama and caddie Shota Hayafuji line up a putt on the first green during the first round.

Hideki Matsuyama and caddie Shota Hayafuji line up a putt on the first green during the first round.

Photo: Mike Ehrmann/Getty Images

For a stretch it looked like Japan’s best male golfer might not even set foot on the course to participate in Japan’s Olympics. Early in July, Matsuyama had to withdraw from a tournament because he tested positive for Covid-19. “I was not sure if I would be able to make it here,” Matsuyama said. 

After 10 days, he began testing negative, allowing him to evade the fate that eliminated world No. 1 Jon Rahm and No. 6 Bryson DeChambeau, who were both knocked out by positive tests. 

But no matter the world rankings—Matsuyama is No. 20—Japan’s homegrown contender was the central figure of the golf at these Games. While his success had already made him an immensely popular figure here for years, his fame rose to new heights just months ago. That’s because the timing of these Olympics happens to follow a seminal moment for Matsuyama and his homeland: At April’s Masters, he became the first-ever Japanese man to win any major. 

The curious thing about that win was that it happened at the same course where the international golf community realized that there soon would be a force to be reckoned with from Japan. A decade earlier, Matsuyama became the first Japanese amateur to compete in the Masters, and the then-19-year-old didn’t simply show up and bask in the azaleas. He outmuscled many of the best golfers in the world. He finished the 2011 Masters tied for 27th, a remarkable showing in which he was the only amateur to make the cut. 

The only reason he had that opportunity in 2011 was because he won another tournament. It took place at Kasumigaseki Country Club. 

The 2010 Asia-Pacific Amateur was just the second edition of a tournament that was created in part to grant an Asian amateur entry into the Masters. There were more than 100 competitors from 27 countries who showed up to the city of Kawagoe to play at Kasumigaseki, which, when it opened in 1929, was the first in Japan’s Saitama prefecture. Later, in 2017, Matsuyama played again at Kasumigaseki with then-President Donald Trump and Japan’s then-Prime Minister Shinzo Abe.

Japan’s Hideki Matsuyama shot a 2 under 69 in the first round.

Japan’s Hideki Matsuyama shot a 2 under 69 in the first round.

Photo: yoshihiro iwamo/Agence France-Presse/Getty Images

When Matsuyama prevailed at Kasumigaseki in 2010, it was a preview into Matsuyama’s major golf fortunes. He shook off final-round nerves to emerge as the champion in a win that would change his life forever. 

This was the beginning of a sequence of events that took him back to Kasumigaseki as one of his country’s most revered sports figures. He starred in the 2011 Masters as a young Japanese amateur because of his win there. A decade later, he went on to win the Masters. Less than three months later, because of a global pandemic that delayed the Olympics by a year, he came back to Kasumigaseki after making that national history. 

The victory at Augusta National was a nerve-racking thrill for Matsuyama and the golf-loving fans who followed his progress through the wee hours of the morning in Japan. A five-stroke lead on the back nine nearly vanished as he sent a shot into the water and struggled to maintain the form that had left him seemingly clear of the field. When he finally sunk his final putt, for a bogey on 18 that gave him a one-stroke victory, it produced a wave of excitement just months ahead of the Olympics here. 

“It was all over the news on every channel,” said Mike Ishizaka, chairman of GolfTEC and founder of the Tokyo-based Golf Digest Online Inc. “It wasn’t just sports—it was headline news. That’s how big of an impact it was.” 

“It was talked about for a month, two months and to this day,” he added. 

That sent Matsuyama and his brand new green jacket to new level of celebrity inside a country where he was already the recipient of intense adulation. It was a national milestone because it was less surprising that Matsuyama won than it was that no Japanese man had won a major before him. There are more than 3,000 courses in the country, according to the National Golf Foundation, and although the sport’s popularity has ebbed because of cultural shifts and its cost, it remains immensely popular.

Hideki Matsuyama hugs his caddie, Shota Hayafuji, on the 18th green after winning the Masters.

Hideki Matsuyama hugs his caddie, Shota Hayafuji, on the 18th green after winning the Masters.

Photo: Kevin C. Cox/Getty Images

The most poignant moment of the Masters victory was also distinctly imbued with Japanese culture. Shota Hayafuji is Matsuyama’s caddie and was two years his junior at the Meitoku Gijuku school. Of all the lessons Akio Takahashi taught his students, there was one that symbolized what a win in Augusta, Ga., meant halfway across the globe. 

“Golf starts with a bow and ends with a bow,” Takahashi said.

Hayafuji listened. He grabbed the flag from the 18th pin. He replaced the stick back in the hole. And before he walked off the final green, he delivered a deep bow. 

Write to Andrew Beaton at andrew.beaton@wsj.com and Miho Inada at miho.inada@wsj.com