Naomi Osaka, this year's U.S. Open women's singles champion, on Monday donated 30 tennis rackets to children in Hokkaido, which was hit by a major earthquake in September.Osaka's grandfather Tetsuo, 73, who lives in Nemuro in the northernmost prefecture, attended a presentation ceremony at the prefectural government office on her behalf."Naomi has been worried about the damage from the earthquake and wants to be of help to Hokkaido. We hope children in the affected areas will enjoy playing tennis," Tetsuo said as he handed one of the rackets to Hokkaido Gov. Harumi Takahashi.Osaka, who star…READ FULL ARTICLE