She made over 150 films in her career, including Miyamoto Musashi and Akō Rōshi.
While attending Amagasaki High School in Amagasaki, Japan, she was selected as Miss Cinderella in 1953 for a “Japan Cinderella Princess Contest” held by RKO Radio & Film Company in conjunction with Mainichi Shinbun.
Crowned as Miss Cinderella, Oka was invited to visit Hollywood and Disney Studios from March 20 to April 4, 1953.
After high school, Oka worked as an office secretary at RKO Radio & Film Company before being scouted by Toei Studios in 1955.
Debuting the same year in Shinsengumi’s The Black Hooded Seer, she quickly gained popularity and was referred to as Toei's "Princess" from the many roles she played as a heroine.