Also, I'm not doing that, that can fuck up a fair few programs. Devs a fucking idiot.
Dev is japanese, makes a game in.... <_<.... >_> japanese unicode then takes that version, translates it into english (assuming this since most japanese devs do this, especially with ALPHA games), but japanese unicode remains, but yes dev is an idiot, because this isn't a common thing japanese devs do.
Also there totally isn't a whole section in tools and tutorials on this exact subject that many people fail to use said tool in said section/other useful tools:
[Tutorial] How To Run Japanese Games On Windows | F95zone even has oh my god you wouldn't believe it other alternatives besides turning your system locale to japanese, specifically this wonderful tool I use all the time called locale emulator.
I'll give you and others one for free too as it's been said several times in multiple threads of japanese games, including this one.
Because they're run in japanese unicode you have to:
A. turn your system locale unicode to japanese (restart your computer), and extract with winrar, or w/e else extractor.
B. You can do the easier option, download bandizip (another zip file extractor program), go to extraction settings, and change the default code page to Japanese, then you can just extract japanese zip files like you would with english ones, and you don't have to change your system locale, sometimes you still have to use locale emulator and run with japanese even after extracting in japanese code page with bandizip.
Alot of this I learned from just lurking on forums and finding helpful guides on search engines.
I have 2 zip file extractors: 7 zip for everyday extracting of zip files (english), and Bandizip for japanese games