You would need a File Manager on your phone to access the save file location for Ren'py on android, which should be Android/Data/com.r3nn.ld/files/saves. There you'd see files named like 1-1-LT1.save etc. I don't know if the name would be different on your phone though but that's where my save files are located on phone. With this, I could transfer save files from phone to pc and vice and versa.
If you also wanna know the save file location for the PC just open file explorer and go to the address bar and copy paste this:
%APPDATA%/RenPy/
Then hit enter and go to the Lustful Desires folder to find the save files.