Okada was born as Satō Kayo (佐藤佳代) on August 22, 1967, the second daughter of the Satō family. The family later moved to Nagoya. In elementary school, Okada loved to read, especially manga, and she was a talented artist. In junior high school, Okada wanted to become a singer and applied for every possible audition, anything from major productions to the smallest talent recruitment, hoping to become a star. She was rejected every time until she was finally accepted to a TV talent program, Star Tanjō! on Nippon Television – similar to Star Search, though the final stage was her singing to get interest from talent agents – singing Kitahara Sawako's MY BOYFRIEND for the audition, and Nakamori Akina's Slow Motion for the final round, which she won in March 1983.