For Walkthrough of Prelude, please check Prelude Forest
After Prelude and following events, you got the Future Diary from Whiskey, listing all your quests, and therefore progress of the main plot since it's a linear game.
You can check your complete and ongoing quests with Diary option in the menu since then.
Here is a list of all the plot relevant quests:
Day1 (start of chapter 1)