If you're playing on a PC, you can find the save files in your User folder, AppData, Roaming, Renpy, Extracurricular Activities folder. So if your username is Joe it would be :
C:\Users\Joe\AppData\Roaming\Renpy\Extracurricular Activities (assuming Windows 10 here). Just delete the files here and it will reset everything.
Not sure about Mac but I believe it's the same principle.
For android, simply delete the APK from the system and it *should* remove the saves. Then you can re-install it.