Looking at the above video with a very young Mizue Takada（高田みづえ）, I thought that she looked like an old university clubmate of mine some 30 years ago. And I suddenly got this hankering for a mug of cocoa.
Anyways, sartorial sarcasm aside, listening to Takada's 5th single, "Purple Shadow" from June 1978, my impression was that the sparky melody could have been ideal for Pink Lady who were riding that huge wave of popularity at the time. So, not surprisingly, I found out the song was composed by Shunichi Tokura（都倉俊一）, the very fellow who had created a number of those Pink Lady hits. Some of that famous Pink Lady choreography could have easily been planned for "Purple Shadow".
The lyrics were by Takashi Matsumoto（松本隆）. I'm not sure what the significance of purple shadows are, so I'm left wondering whether the color has that meaning of uncertainty or something sinister in Japanese songwriting. Takada sings about a woman remembering a fateful tryst between her and a fellow who has since gone somewhere else but may be returning to the old hometown. Suddenly she is filled with a lot of apprehension about a potential reunion with the guy who sounds like a charismatic cad. Getting back to Tokura's music, there is that sense of urgency and drama and not so much of a happy-go-lucky feeling. As Takada sings the title, I even thought that the song would have made for a decent theme for a superhero called The Purple Shadow. "Purple Shadow" got as high as No. 16 on Oricon.