TOKYO — When it comes to U.S.-Japan baseball relations, Ichiro Suzuki is without peer, the pinnacle, the ultimate. No less an authority than Rickey Henderson says so.

“He’s like Elvis, period, here,” the A’s Hall of Famer said. “Ichiro is the legend of all of them. He’s done a lot for the game of baseball, especially for his country and coming to the U.S. and being able to do what he did there. It’s unreal.”

Ichiro is being feted all week at the Tokyo Dome during Major League Baseball’s season-opening series between the Mariners and A’s. The outfielder, a surefire Hall of Famer in the U.S. and in Japan, has become a symbol of the game’s global appeal. As Ichiro approaches his final innings, his presence will continue to be felt as the next Japanese players rise in the U.S., and baseball spreads its borders in Asia and beyond.

Ichiro made his majors debut against Oakland in 2001, and his final big-league game might be Thursday against the A’s.

“I don’t know if there’s been a more impactful player than Ichiro, at least since I’ve been doing this,” said A’s manager Bob Melvin, who has been close friends with Ichiro since Melvin managed the Mariners in 2003-04. “He is beloved in Japan. He’s going to be in the Hall of Fame here. He’s going to be in the Hall of Fame in the U.S.

“It was the first time we saw what Japanese baseball was all about, when he came over here. He’s been an ambassador, he’s been an entertainer and he’s a great player on top of it. He’s one of the most impactful players, for me, in baseball history.”

Ichiro has stated numerous times that he has no wish to retire, but at 45, he’s unlikely to stick in the majors much longer. His influence in both countries cannot be overstated. He kick-started the wave of big-name Japanese players coming to the majors, and his success in Seattle established Japan as a major TV and merchandise market for MLB.

“Even though Hideo Nomo had come over earlier, it really started with Ichiro,” said Jim Small, MLB’s vice president of international business. “There was some resentment within baseball in Japan about him going to the U.S. at the time; I think now that’s gone — the establishment of Japanese baseball wants to see how well those players can do against the best in the world.”

There is a new group of Japanese players in the U.S., including Angels two-way player Shohei Ohtani, last season’s AL Rookie of the Year, and Seattle left-hander Yusei Kikuchi, who will start Thursday’s game against Oakland.

Interest in MLB is healthy in Japan, and in Asia in general. The organization makes about $120 million annually internationally, and the Asian market, which includes Korea and Taiwan, accounts for 70 percent of that. China is emerging as a strong part of the equation, with TV ratings growing, 300 stores licensed to sell merchandise and U.S. baseball academies enjoying success. There are seven Chinese players in the minors, including one of the Brewers’ better pitching prospects, Lun Zhao.

The relationship with Japanese baseball is what helped to open the Chinese market, according to Small, and games such as the season-opening series this week also help — they’re on in prime time, 8 p.m., in China.

“That’s a huge thing for us,” Small said. “Another huge advantage Japan gives us is that the Chinese look at baseball as an Asian sport, not an American sport. That’s a benefit. They want to beat Japan. They want to beat Taiwan. They want to beat Korea. And we’ll help them do it.”

What’s next for MLB? The sport is exploding in New Zealand, which boasts 6,500 players, 30 of whom have played college ball in the U.S., including five who have signed with major-league teams. New Zealand was admitted into the Australian Baseball League last year and QBE baseball stadium will open this fall in Auckland.

MLB has its sights set even higher, though: India and its 1.1 billion population. Small said the league will spend the next three years exploring the market, helping bring baseball programs to schools and taking advantage of TV and social media — 90 percent of the country uses connected devices. Plus, MLB is finding that nations with a cricket background (such as Australia and New Zealand) adapt quickly to baseball.

The A’s, who typically volunteer for international travel, can attest to the value of marketing the sport and the team worldwide. Oakland’s merchandise sales shot up in Japan after the team’s appearances here in 2008 and 2012, and when Hideki Matsui played for the A’s in 2011, each of the games was broadcast in Japan.

In addition, “Moneyball” was one of the most popular movies in Japan when it was released in 2011, and A’s vice president of baseball operations Billy Beane, who was portrayed by Brad Pitt in the film, sees team gear all over the world, including once during a Liverpool soccer game. He made sure to send a photo of the Liverpool fan wearing an A’s cap to Tom Warner, who owns Liverpool and the Boston Red Sox.

This week in Japan, Beane and his family have spotted A’s merchandise on the subway and in shops.

“I was trying to figure out if they were fans coming to the games — or sometimes you can be in a foreign country and someone is just wearing an A’s hat, which is pretty cool,” Beane said. “There are not a lot green and gold teams, so there’s a pretty good chance if you see a green and gold hat, it’s going to be an A’s hat.”

“Moneyball” details the A’s ability to do more with less, looking for undervalued assets to compete with clubs with bigger payrolls, and in the past few years, one avenue to do so has been the international market. Oakland is maxing out its international spending and beefing up its scouting efforts, well, everywhere.

“I love the fact our game has become so international and hopefully there are more countries even beyond Japan where we see players coming from to the major leagues,” Beane said. “There’s going to be a time every major-league team has the entire globe covered. It’s going to happen, sooner than later.”

Susan Slusser is a San Francisco Chronicle staff writer. Email: sslusser@sfchronicle.com Twitter: @susanslusser