For me (Windows XP), just go to control panel, select "Regional and Language Options," go to the 'advanced' tab, and choose Japanese as your 'Language for non-unicode programs." It's been very useful for most japanese indie games (and by extension almost all Ryona games I've found), and shouldn't have any negative effects. And if it does, you can always change it back.
Wait, shit, I actually just remembered what my problem was with the game, I couldn't get it to run until I installed a certain font for it. I just did a quick search for it and found one on hongfire for the game that people say worked, I think it's the same one I used to get it to run. I just uploaded it to mediafire.
knife Japanese Font.rar
I'm terribly sorry for not remembering this earlier.
EDIT: Hey, neat, I like the way this forum handles links.