Just a quick note: You can actually enable syntax highlighting for tagger script in your posts, that makes the script much more readable 
Can you tell which replacements cause issues for you. From what I can see without looking too closely this script defines mostly replacements for characters not allowed in Windows file names, and I am not sure why it does that since Picard will handle this by itself. And there are replacements for a leading dot (also causing issues on all kinds of operating system) and ellipsis. This all should not affect Japanese characters.
On the other hand Picard itself has some options that affects non latin characters. Check your settings in Options → Metadata, especially “Translate artists names to this locale where possible”, “Use standardized artist names” and “Convert Unicode punctuation characters to ASCII”.
What I wrote here pretty much applies to this as well.