Japan’s Naomi Osaka, a four-times Grand Slam tennis champion who has helped raise awareness of mental health issues in sport, is the world’s highest-paid female athlete, according to a list published by business magazine Forbes on Thursday. Osaka raked in $57.3 million in prize money and endorsements over the last year, nearly all of which came from an endorsement portfolio that has added more than 10 brand partners over the last year and a half. The list was published after a year in which Osaka withdrew from the French Open to focus on her mental health amid a public row over mandatory press conferences at the Grand Slam, saying they took too great a toll on her mental wellbeing. Fellow tennis players Serena Williams (45.9 million) and older sister Venus ($11.3 million) were next on the list. American gymnast Simone Biles ($10.1 million) and Spanish tennis player Garbine Muguruza ($8.8 …