You can join the discord server. You will find there several save folders.
If you want to just delete the Free Mode progress, you can do it by: going:
C:/User/User_Name/AppData/LocalLow/NymphoKyun/Slavebar
Savefiles for Story Mode are ended in ".dat_s" and those for Free Mode are ".dat"
Extra: After completing every event on Free Mode, you will unlock the "Event Selection" menu in your house. That way you can repeat any event of your liking