Sounds like the save data got corrupted somehow, if you're on Windows you can go to "AppData/LocalLow/tian nya/WOWOWOW KORONE BOX" (you can go to your AppData folder quickly by typing "%AppData%" and exiting the "Roaming" folder) and delete "saveData.json" to reset. If possible, see if you can post the contents of the file here (use Notepad to open) so I can take a look.