Nao Oikawa was born in Hiroshima, Japan on April 21, 1981. Her family moved to Tokyo when she was a little girl.
At age 18, when she graduated from high school and began to go to design school, she met a scout man who proposed her to be an AV idol.
AV producers did not think that she had special talent in their genre. She used her time for studying popular porn stars' acting. Finally, Oikawa made her debut adult video at age nineteen for the Media Station Cosmos Plan label in September 2000.
Oikawa has been able to use her fame in the AV industry to enter mainstream media work.She made a guest appearance in the 6th episode of GARO. It was her first appearance on Tokusatsu sfx series. GARO's action director Makoto Yokoyama says Oikawa's supple body is suitable to sfx action.
Oikawa played the role of villainess Kegalesia in the TV Asahi tokusatsu TV series for kids Engine Sentai Go-onger.
She also appeared in the Kamen Rider Decade epilogue portion of the December 2009 film Kamen Rider × Kamen Rider W & Decade: Movie War 2010 as the Bee Woman of Shocker.