I would be careful, it seems installing the latest android version had wiped all my saves.
My bad really for not backing them up first, so, back up your saves before installing
Open your file manager, whatever that may be called on your device, then navigate to the file containing your saves....internal storage/android/data/com.cryoxxx.oppaiodyssey (may be different on your device). Then literally copy the 'saves' folder to another custom folder, personally I copy them to a folder on my SD card.
Then, if ever you have to do a reinstall for example, just copy the save file from your SD card and replace the one in the games route directory.