We've been digging into this obscure little web game from way back when. Its essentially a HTML page with a shockwave clip and brief description in Japanese.
The actual SWF game itself is a Puyo Puyo version of a pachislo slot machine, you gain 100 credits and have to match 4 puyos of the same colour so they disappear, the game ends at 300 points (originally you could download it from Sonicteams website when you reached that amount) and you play again.
I originally came across this through the old Insertcredit site (not the rather moribund new version) when I first joined the Internet age, 10 or so years back. It was to promote a Dreamcast version of Puyo Puyo Fever along with a slider puzzle (that old make the picture by sliding tiles) and various wallpaper. We had this on our old PC along with some other stuff and forgot all about it. Clearing out our old PC we found this and decided to give it a translation, and alter the graphics so they read in English. I'm not sure what you'll need to alter the SWF file, but Libre Office can handle the webpage side of things, and that is mainly done now. All it needs is the text cleaned up and its ready to play.