TOKYO — When the Ohno family watched Naomi Osaka beat Serena Williams at the United States Open early Sunday morning from Tokyo, there was no question in their minds that Ms. Osaka was a true Japanese champion.
“Her face looks Japanese,” said Ryutaro Ohno, 14, shortly after playing a few tennis matches with his younger brother and parents at a court near the base of Tokyo Tower.
His mother, Naoko, 49, showed a snapshot on her cellphone of her sons posing with Ms. Osaka, the daughter of a Haitian-American father and Japanese mother, when the tennis star played in the Pan Pacific Open in the Japanese capital last year.
“Her soul is Japanese,” said Ms. Ohno. “She doesn’t display her joy so excessively. Her playing style is aggressive, but she is always humble in interviews. I like that.”
Her emergence comes at a time when Japan is also grappling with a declining population, a looming demographic crisis that has prompted the country to open its doors slightly to accommodate an…