OK, I found my copy, and I think I know how to sort this out.
Basically, ignore the setup programs. You should be able to make to game run by going into the GAMEDATA folder and double-clicking system35.exe.
There is a slight complication in that system35.exe reads SETUP.INF in the folder above to find the filenames for the game itself. The problem here is that if the archieve is unpacked without support for Japanese characters, the filenames can get mangled so it still fails.
The eaiest solution is probably to backup setup.inf and then edit the names to match the ones in the GAMEDATA folder.You can generally match them up on the the last two chars of the name, plus the extension. You may need to rename the data files as well as the matching lines in setup.inf.
Once all that is done. double-clicking system35.exe should launch the game.
Beyond that ... there used to be an excellent explanation of all this on Hentai Palm before a certain mad moderator decided to delete everything in sight. Sadly, I don't know where you'd find a better discussion now, although asking on HP or Hongfire would probably work.