@Bryanis
Problem is, I get the very same option I got as shown in my attached file, for Dame Zettai 0 too... And after checking, I have nearly nothing changed in firefox's about:config regarding flash... And after changing those back to defaults it still let me commence with the "Allow" part. Try installing the latest adobe flash for your system?
Also, I'm in non-Japanese locale, Win8.1. Might be worth getting back to your regular locale for the installation of Adobe Flash, so that you may actually know what's going on (cos I assume it's in Japanese on default if you are trying to install it while being in Japanese locale?).