She made her songwriting debut in 1985 with Kanako Wada's "Passing Through", which won the Mitsubishi Minica Mascot Song Contest.
[1] During her time with Fuji Pacific Music, Oikawa wrote songs for numerous Japanese idols; most notably the duo Wink.
[2] Oikawa's most well-known song outside Japan is "A Cruel Angel's Thesis", recorded by Yoko Takahashi for the 1995 anime series Neon Genesis Evangelion.
Combined with the royalties from the Evangelion pachinko machines, Oikawa receives no less than ¥30 million annually from the song alone.
Oikawa published her biography Hakon (破婚, Breakdown), which detailed the last days of her marriage.