1. open the control panel and navigate to clock language and region --> region --> administrative --> change system locale
2. a box will pop up asking to select which language u want, scroll until you find "japanese (japan)" DONT ENABLE UNICODE UTF8 It will ruin what ur trying to dothis will not change the language on your computer only makes it so files will not be gibberish so dont worry about it turning the language into japanese
3. click OK and let it restart the computer when it asks you
4. download the RTP (Runtime package) for the game u want to play. the rtps for japanese games are here and the rtps for english games are here. if u dont know what kind of rpg maker version ur game was made in u can probably search it up or it was mentioned on the download page
5. install the rtp, u probably shouldnt change the directory it chooses
6. extract the game u want to play and run RPG_RT.exe (some games have a unique executable named start.exe) it'll probably be in fullscreen if you use RPG_RT so if u wanna get out and be in windowed press alt+enter Pressing once will make it a medium size window pressing twice will make it the smallest size
that is seriously really it. all u need to do is change the locale and install the rtp also i can't remember if this is a requirement or not but 7zip is a good program to use when extracting files Can unzip .rar and .7z files among other things