MILL VALLEY, California (Kyodo) — A new documentary about baseball connections between the United States and Japan delves into the sport’s role across more than a century of history as the relationship between the two nations grew and overcame a painful period of war.


Yuriko Gamo Romer’s “Diamond Diplomacy” had its world premiere on Friday at the Mill Valley Film Festival in the San Francisco area.


Romer, 68, who is Japanese American, said the release of the film in the works since 2014 comes with perfect timing, as “there has never been this much general awareness (in the United States) of baseball in Japan and Japanese baseball players” such as Los Angeles Dodgers star Shohei Ohtani.


Baseball was first introduced to Japan by an American in 1872. Since then, the shared love for the game across the Pacific has helped grow and, after the United States and other Allied countries defeated Japan in World War II, heal the relationship between the one-time foes.


The documentary chronicles major chapters in the baseball history between the two countries, including Major League Baseball legend Babe Ruth’s visit to prewar Japan in 1934 and the sensation that ensued after Japanese star Hideo Nomo, known for his “tornado” corkscrew delivery, debuted as a Dodgers pitcher in 1995.


The film shows how players such as Nomo and Warren Cromartie, an American who played for the Yomiuri Giants in Nippon Professional Baseball for seven seasons until 1990, contributed to “person-to-person diplomacy” between the two countries as goodwill ambassadors.


One player heavily featured in the film is Masanori Murakami, the first Japanese to play in MLB as a San Francisco Giants pitcher between 1964 and 1965.


“I was very moved,” said Murakami, 81, after the screening.









Yuriko Gamo Romer, left, director of the documentary “Diamond Diplomacy,” speaks alongside former professional baseball player Masanori Murakami at the film’s premiere in Mill Valley, California, on Oct. 3, 2025. (Kyodo)


The inspiration for the documentary came when Romer learned that in 1949, just years after the war, a minor-league squad called the San Francisco Seals toured Japan playing teams across the country. The little-known episode from baseball history got her interested in the subject.


Jack Bair, 61, chief development officer for the San Francisco Giants who has worked with the team for 33 years, said after the screening that it was interesting to know just how much baseball played a role in repairing the ties between the two countries after the war.


The connection between the United States and Japan through baseball has only become more pronounced with the popularity of Japanese players like Ichiro Suzuki, who this year became his country’s first-ever inductee into the U.S. Baseball Hall of Fame, and Ohtani, currently seen as the face of MLB.


Since its launch in 1977, the Mill Valley Film Festival has become known as a “filmmakers’ festival” showing international and independent films, including ones produced by well-known studios. This year’s festival runs through Sunday.


“Diamond Diplomacy,” Romer’s second feature documentary, is now set to be screened at a handful of other film festivals across the United States.


(By George Galer)