Instead of futzing around with restart-requiring system locale changes or unzip programs that were made never expecting to be used on files in another language, follow the instructions in this post: How to machine translate Japanese RPG maker games
The program “sjisunzip” handles unzipping Japanese files with no fuss.
The forum actually warned me that the link above was already posted in this thread before, so it’s not the first time this specific game has given people this problem…