Since iOS offers no direct file access, these instructions are for (non-rooted). Older Android versions are even easier.
Grim Soul operates on a hybrid system. Your device (the client) stores local cache files that allow the game to run smoothly, but your actual inventory, level, and base location are stored on Kefir!’s remote servers. This synchronization prevents players from easily hacking the game by modifying a local text file, as the server will reject changes it doesn't recognize. Grim Soul Save Data File Download