Can't open filenames with mix of japanese & english characters

[Ruriko]

Is there a way to make avisynth open filenames with mixture of jap & eng characters? cause I don't want to rename them

[qyot27]

Use a source filter that supports UTF-8 (FFMS2 does), save the AviSynth script as UTF-8 without signature (Notepad2 can do this).

For optimum results, make sure the *.avs filename doesn't mix characters, since some programs don't like that (VirtualDub seems to handle it, ffmpeg and mpv do not). A trick to make this work is to create a symbolic link that directs to the mixed-name *.avs file, but make the symbolic link use only ASCII characters.

[pinterf]

Avisource (http://avisynth.nl/index.php/AviSource), AviFileSource, OpenDMLSource, WavSource have utf8 support as well (parameter tells that file name should be handled as a utf8 string)
Other filters which can handle utf8 in this hacked way qyot27 mentioned: Import (http://avisynth.nl/index.php/Internal_functions#Import) (file name), Subtitle (the text itself).
(Avisynth+ specific)