Windows: 2 locations...
Game\Saves\
C:\Users\YourWindowsUserName\AppData\Roaming\RenPy\Lewd Town Adventures\
Android - much more complicated. You need to access hidden system files using a File Manager and locate the app data, locate the save files directory, then delete them manually.
OR! Simply save OVER (overwrite) the save slots you do not want to keep.