First you must go to your DDLC steam folder (which can be accessed by right clicking Doki Doki Literature Club in your Games Library, clicking Properties, Selecting Local Files on the top bar, and selecting Browse Local Files). However you don’t need to reinstall the game or whatever it’s very simple to fix this and get back to the start of the game. If this is your situation, then evertime you launch the game it will place you in the room with Monika and there isn’t really anything you can do about it because you are not able to access the main menu. Now if you ended up with the Just Monika ending then this will be important for you, but if you already have a fresh game ready then you can ignore this section.
Skip if you already have a clean game ready to play or have not played it yet.
Next I will talk about how to begin your playthrough to actually beat the game instead of getting Monika in some void or whatever. My experience: I did a blind run of the game, no save reloading or anything just balls out making decisions and I ended up with the usual ending that one receives after a straight playthrough, which can be summed up as Just Monika, everyone else had been deleted and I didn’t really know what to do from there and the game messed with my head. Well, I created this guide for the purpose of helping other players make everyone in the literature club happy! So you either have completed a blind run of the game (and you really want closure and for everyone to be happy), or you just want to get the best ending.