Edit: v1.04 changed the save to be a standalone file located at Steam\userdata(steam id number)\2459750\remote
This game does not offer a native way to delete saves, and the save is located in the registry instead of a standalone file.
To backup a save game open Registry Editor and go to Computer\HKEY_CURRENT_USER\SOFTWARE\BeXide\Yohane the Parhelion - NUMAZU in the MIRAGE - and in the upper left corner go to File > Export. When you want to restore that save go to File > Import in the same location.
To reset your save, go to the same location and delete all of the files there (it's okay if (Default) is still there). When you open the game again, it will act like a new save file.
Runs shorter than 30 minutes may be rejected for not showing the Strategy Bonus menu before the run.
This is because it's possible to get the same or similar effects from the starter charm as a sub effect which would be extremely easy to cheat if the menu is not shown, while not alienating new runn