libfatのソース見たけど 〜\libfat-src-1.0.3\source\directory.c if (_FAT_directory_ucs2tombs (entry->filename, lfn, MAX_FILENAME_LENGTH) == (size_t)-1) { // Failed to convert the file name to UTF-8. Maybe the wrong locale is set? return false; } UTF8に変換してるんじゃないの