A point guard, Oga played for the JX Sunflowers in the Women's Japan Basketball League and the Phoenix Mercury in the WNBA.

[10][11] For the 2015 season she returned to Japan, signing with the Toyota Antelopes, where she played until her retirement in 2018.

[9][12] In 2007, she became the first Japanese female player to sign a professional contract in the domestic leagues.

She recorded 4 points and 1 assist in her WNBA debut on May 17, 2008, in the season opener, a 94–99 loss against the Los Angeles Sparks.

While Japan only finished tenth, Oga was the high scorer for the tournament, averaging 19 points a game.