How can I open files that have Japanese filenames? I organize my Japanese ebooks and manga using the respective Japanese titles as filenames.  I then access this content from my Anrdoid device by mounting a cifs share with cifsmanager. However I cannot open the media using my Android 4.1 (AOSP) device. The non-ascii characters in my filesystem show up as just question marks, e.g. /mnt/sdcard/manga/??????/.  The error behavior that various apps will give range from File does not exist (File Manager) to nothing at all (PerfectViewer).
You are facing this issue because (as @liamwli said) you lack the required font and also possibly because of lack of sufficient libraries in your present ROM.
Due to this reason, it is unable to display the file name properly and as a ramification of this issue, different apps behave differently based on how the developer handled this situation.

What can be done?
This depends on few factors:
If your phone is rooted, extract DroidSansFallBack.ttf from /system/fonts folder to your computer and examine whether it has the required characters in Japanese. I assume you can read Japanese. This is to ensure the first part of the reason explained in &quot;why&quot; section.
If you do not have Japanese character displayed, please try finding a suitable TrueType Font (TTF) which displays Japanese characters in PC. Copy this file to the above said folder with DroidSansFallBack.ttf, replacing the existing file (after backup). After a reboot you may be able to see characters properly. Then the apps might be able to open the file.
In case if you are still unable to open such files, please revert back the backed up TTF file.