Four-time Grand Slam singles champion Naomi Osaka began playing tennis when she was three years old. She worked hard in her lessons to improve, leading her to become a pro player at just 15 years old! Osaka rose through the ranks and competed against great players. In 2018, she even won against tennis legend Serena Williams at the US Open. Follow Osaka's tennis journey, from her first lessons in New York to her wins at international competitions.