Osaka was born in Osaka, Japan to a Haitian father and a Japanese mother. On 1 February 2016, Osaka reached her best singles ranking of world number 108. On 1 December 2014, she peaked at world number 1269 in the doubles rankings.
Osaka made her main draw WTA tour debut at the 2014 Bank of the West Classic, having firstly entered the qualifying tournament and defeating Alla Kudryavtseva and Petra Martić for a spot in the main draw. She was then pitted against 2011 US Open champion Samantha Stosur and came from a set down to defeat the Australian in a match lasting two-and-a-half hours. It was Osaka's first ever main draw match win at the WTA level.
Won tournament; reached the Finals; Semifinals; Quarterfinals; Rounds 4, 3, 2, 1; competed at a Round Robin stage; reached a Qualification Round; absent from tournament event; played in a Davis Cup or Fed Cup Zonal Group (with its number indication) or Play-off; won a Bronze, Silver (F or S) or Gold medal at the Olympics; a downgraded Masters Series/1000 tournament (Not a Masters Series); or a tournament that was Not Held in a given year.
To avoid confusion and double counting, these charts are updated either at the conclusion of a tournament, or when the player's participation in the tournament has ended.