This speech synthesizer outputs human voices with some of the Jast software. It is compatible with FM-7/FM-New7FM-7/MSX/PC-8801/PC-8801mkII/PC-8801SR/X1. A different cable was provided for each platform.
Price: 12800 yen
PC-8801 Afternoon Angels videos: https://www.nicovideo.jp/watch/sm2223243 https://www.nicovideo.jp/watch/sm2250712
Homebrew guide: http://kitahei88.blog.fc2.com/blog-entry-87.html
The MSX version is not confirmed to exist. There is neither witness nor photo and most ads do not include MSX in their platform list.