HIDETO SAKAI AS they celebrated Naomi Osaka's victory in the final of the U.S. Open in Flushing Meadows on Saturday, Tokyoites were eager to embrace their heroines' stand against racial injustice. Osaka, who won her third Grand Slam title with victory over Victoria Azarenka, has used her platform to support the Black Lives Matter (BLM) movement, wearing a mask bearing the name of a different Black American before each of her seven matches in the championship. Osaka, who has a Japanese mother and Haitian father, has become the face of a changing Japan coming to terms with challenges to its…