Japan’s Naomi Osaka said Friday on Twitter that she has returned to training after taking a break since her third-round exit at the U.S Open in September. “Kinda rusty but feels good to be back. I really want to say thank you everyone for all the kind messages, I really appreciate it,” the former world No. 1 tweeted with emoji and photos of herself and a racket. The four-time Grand Slam champion pulled out of the French Open in May ahead of her second-round match when she decided not to attend a press conference and revealed her struggle with depression. She sat out Wimbledon before participat…