Obviously spoilers:
MC replaces OG Villainess before the plot snowballs but the OG Villainess possesses the OG Heroine and white lilly’s everything until she’s so stupid she just dies like three times. MC and her Guy BFF are endgame but he also has memories before the regression? And falls in love with MC in the body of his villainess BFF? And still tries to help his OG Villainess BFF even though she has basically tried to ruin MCs life and kill her. Ruining MCs life doesn’t work for her so she literally offs herself. OG Heroine comes back. OG ML is in love with MC now despite absolute foolishness. Prince—who is trying to play checkers with OG Heroine while she plays checkers—is also in love with MC. Filler hijinks happen and MC and Guy BFF get married while OG Villainess gets isekaied into modern times and falls in love (with maybe OG ML?). There’s a whole bunch more filler and conversations that can only happen if you’re writing a salty fanfic at like 14. But that’s all of the PLOT.

Unless you read this when it was still publishing weekly don’t even bother, it’s so stupid. If you did start it way back when and want closure or something? Don’t bother. It’s stupid. Read it years ago and forgot about it so you wanna reread? Yeah no it’s worse than you think. Read something that doesn’t feel like it was written by a group of 10 year olds.