GS_Pack is the command-line extractor/packer for data pack format used by the game Griefsyndrome, as an alternative tool for GropeSyndrome.
This tool uses the correct Code Page to decode the file name in the package, giving you the correct name for all files, for example, data/system/StageMain/HPバー.cv2.
This tool is written in C# so it's easier for someone who have only the binary to obtain the source code by decompiling.