Japanese tennis star Naomi Osaka has become the highest paid female athlete in the world, topping American great Serena Williams.According to the Forbes magazine, Osaka earned $37.4 million in the last 12 months from prize money and endorsements, $1.4 million more than Williams, setting an all-time earnings record for a female athlete in a single year. Maria Sharapova previously held the record with $29.7 million in 2015.