Yes! You can reset all your save files by locating the RenPy directory and deleting/moving the entire "14DaysWithYou" folder! Depending on what sort of PC you use, you can find the folder in:
Windows: %APPDATA%/RenPy
Mac: ~/Library/RenPy
There should be a folder inside your RenPy directory called "14DaysWithYou[0000XYZ]". The numbers will be different depending on the version you've downloaded, but it shouldn't really matter.