Here's what I can advice if your playing on android, since you will have to uninstall the old version before installing the new update.
get your save files from Android>data>com.niichan.mbml>files>saves
copy your saves folder to anywhere you want to place it. Then uninstall the old version and install the new one. Open the game for bit, then close it. proceed to place the copied save files to the original location, and your good to go.