Yami to Koe and Yami to Koe 2 are those kinda games that basically can't be installed on modern OS'. I had the same problem with both of them, that being the exact same as mailman over here, and gave up on the traditional methods of installation. What worked for me was to install Windows Virtual PC with XP mode. Download the Virtual PC software and the Japanese version of the XP mode and install in that order. From there do as you would on your current OS: mount the file using daemon/alcohol/whatever and run the installer.