 | Check out the Rare Gaming Dump YouTube channel and the Rare Gaming Dump Discord! |
JSys is Nintendo's in-house framework they use to make their games, including GameCube, Wii, and probably other consoles such as the 3DS. It probably has support for the SZS (aka Yaz0) compression format, and BMG and MSBT message files. JSys is used in most first-party developed games.