“It kind of embodies the very muscular kind of power that he likes,” said Sheila A. Smith, a Japan expert at the Council on Foreign Relations. “It’s maybe a more comfortable and interesting setting for him than some of the more pomp-and-circumstance red carpet settings.”

The spring basho runs for two weeks, and there have already been some upsets. The final is likely to be a nail-biter, with the championship expected to come down to a battle between a Japanese wrestler and a top-ranked Mongolian wrestler, whose countrymen have dominated the sport for almost two decades.

Seasoned sumo watchers say the prominence of foreign-born wrestlers shows that the sport has in some ways been at the vanguard of Japan’s incremental globalization.

Sumo wrestlers from Hawaii came to Japan in the 1980s, and champions from Bulgaria, Georgia, Estonia and Mongolia followed. There has been some backlash, but for the most part, Japanese fans have embraced the new champions.

“Sumo, which is the most Japanese of sports, was under no pressure to do so, but opened its doors to foreign workers decades ago,” said John Gunning, an Irish-born, English-language sumo commentator on NHK, the public broadcaster, who represented Ireland in the world sumo championships.

“There might be an image of them being an old, stuffy, conservative organization, which is an accusation that has some merit,” said Mr. Gunning, who also writes a sumo column for The Japan Times. “But in general, they have led the way and shown Japan this is what can be done and the world doesn’t come to an end just because you let a few foreigners in.”