Twenty-five years ago, in April 1999, there were six Japanese players on Major League Baseball rosters. Hideo Nomo was the most famous of the bunch, but there were other names, too. Masato Yoshii, Hideki Irabu, Mac Suzuki and Shigetoshi Hasegawa ended up pitching at least five MLB seasons. They were big leaguers and trailblazers. But they were rarities in MLB, which by and large still treated Japanese players as though they had something to prove.

A quarter-century later, Japanese stars are integral parts of MLB’s story, playing prominent roles on prominent teams and commanding as much attention and money as, if not more than, North American-born stars.

The highest-paid hitter in the majors, Shohei Ohtani, began his playing career in Nippon Professional Baseball. The highest-paid pitcher, Yoshinobu Yamamoto, earned his deal entirely based on his track record in NPB.

Chicago Cubs left-hander Shota Imanaga has looked dominant. New York Mets right-hander Kodai Senga finished second in National League rookie of the year voting last season. In an era of fleeting starter durability, San Diego Padres right-hander Yu Darvish is sixth among active pitchers in career strikeouts. As many eyes are on young Japanese righty Roki Sasaki, who is still pitching for NPB’s Chiba Lotte Marines, as there are on any elite college player who might find himself drafted this summer.

The change came slowly, then swiftly, unleashing a torrent of Japanese talent coming stateside that will only pick up speed. And according to conversations with more than a dozen current and former NPB players, coaches and MLB executives, a shrinking world and changing attitudes combined to make it possible.

“I think overall, maybe 10 years back, the understanding for players in Japan was that it was going to be tough to make it over here,” Darvish said through an interpreter. “But I think the hurdle has become a little bit lower — or, maybe, it’s the other way around: Players over there are getting better, then doing a better job when they come here.”

When Darvish debuted in 2012, Japanese players finding stardom in the United States still qualified as a rarity. The first Japanese standout to make the leap was reliever Masanori Murakami, whose promising MLB career began with the San Francisco Giants in 1964 and ended a year later when a contract dispute with his NPB team forced him to return to Japan.

It was three decades before an NPB standout would find his way to MLB again, when Nomo grew frustrated with the way his Kintetsu Buffaloes were using him and found a loophole that allowed him to make the jump to the Los Angeles Dodgers in 1995. His success signaled that Japanese aces could fare well in the United States, too, and pushed the leagues to establish the posting system, which allows Japanese stars to sign with MLB teams and Japanese teams to be compensated.

A few years later, Ichiro Suzuki arrived, and in the years that followed stars including Daisuke Matsuzaka and Hideki Matsui inspired bidding wars among some of baseball’s most storied franchises. But for the most part, the trickle of talent across the Pacific was slow and limited to NPB’s elite players — or, at least, those who were most certain they would find success here.

In the years since, though, Darvish arrived and thrived. Starters including Masahiro Tanaka, Kenta Maeda and Yusei Kikuchi waited out the requisite six years in Japan before heading to MLB and establishing themselves as valuable assets. Little by little, the question for top NPB talent changed. It is rarely a question of whether they will make the jump to MLB but rather when they will make it.

Ohtani was so good, so soon, that he did not even wait until he was eligible to head to MLB and instead made a deal with his NPB team to come over early. In the years that followed, players such as Seiya Suzuki and Masataka Yoshida found an MLB market willing to bet on Japanese hitters, too.

Darvish, meanwhile, emerged as something of a stateside mentor, the person Japanese pitchers would call for advice about whether they could make it here and how. The evolution of that role coincided with an unmistakable shift in posture for young Japanese players: Once, the stars who made the jump from NPB felt like untouchable heroes who sneaked through a door open only to the elite. Then, slowly but surely, their success started to prop that door open and show others how to follow them through it.

“The trend of Japanese players wanting to come play across the ocean started with the legend Ichiro. Everyone looked up to him. More recently it’s Darvish; he played a big role. Then came Ohtani. And I think more and more Japanese players are coming over, and everyone is looking up to them,” Senga said through an interpreter. “Because they look up to them, they want to come over here.”

The more Japanese players see themselves in MLB, the more they start to build themselves to the specifications MLB prefers. The more MLB sees Japanese stars thriving in its ranks, the more it starts to look for them. The century-old exchange of baseball culture, it seems, has reached a new, and in some cases very, lucrative apex.

Last week, the Baseball Hall of Fame announced an upcoming exhibit that explores the shared baseball history of the United States and Japan, an addition to the museum’s collections that will open next summer. The exhibit was planned to coincide with Ichiro Suzuki’s first appearance on the Hall of Fame ballot, which is fitting: When the results of that vote are announced in January, he almost certainly will become the first Japanese player to be elected. It has never seemed so certain that others will follow.