The .rar extension requires software like WinRAR or 7-Zip for extraction.
These files are usually loaded via the KH1 ReMoD or LuaBackend tools. Users place the extracted .pkg or .assets files into the game's ~mods folder. V_KH1-4.rar
While the exact contents can vary depending on the uploader, this specific file naming convention usually points to a comprehensive "Vanitas" asset collection: V_KH1-4.rar