She had been seen as the second Seiko Matsuda（松田聖子）: all of her singles had peaked at no less than No. 20 on the Oricon weeklies, and a number of her songs had been composed and/or written by popular artists such as Mariya Takeuchi, Ryuichi Sakamoto, and EPO. And her most successful song, "Kuchibiru Network", was written by Seiko herself. Outside of music, she starred in a TV drama and several commercials. Professionally, it seemed that the world was her oyster.
However, as many fans of 80s aidoru know, it all ended very sadly when for reasons that remain unknown, Okada committed suicide in April 1986. The news of her death reached huge proportions in Japan, and even reached as far as my city. I'm not sure how I found out...no Internet back in those days, so I can only conclude that it was either a news report on TV or in the papers. Even more horrifically, copycat suicides occurred in the days after Okada's death to such an extent that one of her family (her mother, I believe) appeared on TV to implore a stop to any more tragedy.
"Kuchibiru Network" was her most successful song but I wanted to feature this one, "Lonesome Season" since I hadn't ever heard the original version before tonight. I actually have listened to the cover by Mariya Takeuchi（竹内まりや）, who had written and composed the song. Although "Kuchibiru Network" has that feeling of aidoru, I found Okada's "Lonesome Season" to have a more mature delivery to it, following the way that Takeuchi sings her ballads in that dramatic, lilting fashion.
"Lonesome Season" was a track on Okada's 3rd album, "Juu-gatsu no Ningyo"(十月の人魚...October Mermaid) released in September 1985.
Considering how she has remained loved on sites like YouTube and Flickr, she does seem to have posthumously earned the label "The Eternal Aidoru".