The 2000 game Power Pro-kun Pocket 2 for the GBC credits four people with sound, all names in hira:
Yuichi Sakakura (坂倉 雄一?),
Junko Sunago (砂子 純子),
Naoyuki Sato, and then a Saiko Toyohara (とよはら さいこ). Saiko seems to be a relatively uncommon name and this is later than all works of Saiko Miki I know of, so my guess is she got married and changed her name, but obviously I can't prove that.
The only VGM-related hits to that name I could find in English or Japanese are for Power Pro-kun Pocket 2, so I wouldn't rule out a (widespread) transcription error as a possibility.