If you locate the game's save files (the location will be dependent on what platform you are playing on and your operating system) and make a backup and then try to restore it after the game wipes all the in-game saves (e.g. Manipulating the game files in certain ways can cause Monica to scold you in-game.
Some of them (such as Yuri's character file) have to be Base 64 decoded. They are also deleted as the game progresses, so if you wish to save them it is best to create a copy of them outside the game directory. The messages themselves are created at random points and a player may not see the same ones in various playthroughs.
Periodically throughout the game, text messages will be created in the game's directory - reading them can reveal special messages from Monica.
