It's due to a UTF8 to ASCII issue. ASCII characters only use one byte where as UTF8 uses two. When the game is compiled in Unity it's done so with a Japanese code page. The way to fix this would be to decompile the game, change the code page, and then recompile the game. A better solution would be for the games maker to add a language plugin with flexible code pages. I can't figure out all the missing libraries, what the assets are packaged with, or how to setup Unity for such an operation so I can't do this. The games maker may also be using Dotfuscator which would compound the issues.
I released a translation file a few posts back that adds more text boxes so you don't lose text. It doesn't fix the spacing issue nor the crash in a later mission. The Unity version has more scenes and continues the story for quite a while while being uncensored. The machine translation doesn't kick in until the end of the original game segment. Unfortunately the level gap only increases and I reached a stall out as I couldn't over level enough to continue with only two characters. Until the game maker releases a version with a select-able code page, I'm going to hold off on finishing the game.