I knew that Miho Morikawa（森川美穂）started out as a mid-1980s aidoru before going into power pop although I'm not sure when the turning point was.
However, I'm pretty certain that the transition was complete by the launch of her 4th original album "1/2 Contrast" in June 1988. I've been listening to some of the album and it seems as if Morikawa partly opted for a party atmosphere in the tropics as a theme...kinda along the same lines of Akemi Ishii（石井明美）. Not a bad way to begin the purely pop phase.
The first track is "Splash Blue" and it sounds like Morikawa was enjoying a major cruise on the Love Boat. With a happily danceable (secretly anyways) Latin-tinged arrangement by Shingo Kobayashi（小林信吾）for Minoru Komorita's（小森田実）melody and Keiko Aso's（麻生圭子）lyrics, this is about as active a Resort Pop as I've ever heard, and Morikawa's vocals here are the ones that I was introduced to when I first heard the singer on her "Blue Water" in 1990. As for "1/2 Contrast", it peaked at No. 17 on Oricon.