You'll have to delete the two Persistent folders (one the game folder and one in the computer system folder). If you only delete one or only the save files it won't work:
If you want to play again with a full reset, you'll have to delete ALL save/persistent data from TWO game files:
-- one in the folder where you installed the game
- Delete ALL save/persistent data in the save folder
-- AND one in these platform-specific locations on your computer:
- Windows: %APPDATA%\RenPy
- Macintosh: $HOME/Library/RenPy
- Linux: $HOME/.renpy
Look for the 'DoNOTTakeThisCatHome' folder and delete ALL save/persistent data in it