But Tokyo itself remains remarkably monochromatic. According to the city government, only about 4 percent of residents were born outside Japan – about twice as many as in the country. (In contrast, more than 35 percent of London and New York residents were born abroad.)

Marie Nakagawa, a former Senegalese-Japanese model, said she felt like a “foreigner” who grew up in Japan. Even today, she regularly endures shouts from men saying she is a doorbell for Ms. Osaka, whose advocacy for racial justice has forced the country to confront a problem that many here think does not apply to her.

Basics of the Summer Olympics

“I hear experts say all the time that things have changed since Naomi Osaka, but the tyrants are still the same,” Ms. Nakagawa said. “You weren’t reeducated.”

In 2019, when Ms. Osaka won her second Grand Slam at the Australian Open, Nissin featured her pale skin and brown hair in a marketing cartoon, leading to whitewash allegations.

“It’s obvious that I’m tanned,” Ms. Osaka replied. Nissin apologized.

Takeshi Fujiwara, a sprinter who specializes in the 400 meters, grew up in El Salvador, where his Japanese name raised his eyebrows. His mother is from there and his father is Japanese. Even after Mr. Fujiwara took part in the Olympic Games in Athens for El Salvador, the whispers about his nationality continued.

In 2013 he switched his loyalty to Japan and moved to his father’s homeland. The greeting was not immediate, he said, even if people commented positively on his “macho-macho” muscles.

“When I came to Japan, I thought, ‘Hey, I’m here in my country.’ They said, ‘Hey, where are you from?’ ”Said Mr. Fujiwara. “It’s gotten better, but we’re still a long way from a place where multiracial Japanese are considered normal.”