File name with multi-byte character isn't processed properly

When I run the following command with file name included multi-byte character on Command Prompt,
Error occurred and wasn't processed properly.

> multimarkdown FILENAME
> Error reading file 'FILENAME'
>
> multimarkdown "FILENAME"
> Error reading file 'FILENAME'

Where FILENAME is `MultiMarkdownの使い方.md`.

When I change FILENAME with `HowToUseMultiMarkdown.md`, it seems to be processed properly.

MultiMarkdown 5 goes well, but MultiMarkdown 6 (6.2.3) doesn't go well.

At MultiMarkdown 6, file name with multi-byte character is NOT supported ?

I use Windows 10 Professional Fall Creators Update, 64bit.