Kingdom Hearts 1:
The antagonist is your best friend Riku. Surprise, it's actually Maleficent! Surprise it's actually some guy named Ansem. Well at least they're all dead now.
Kingdom Hearts Chain of Memories:
Here have 6 new villains. A whole Organization! They're ask dead now. Wait Riku's alive? And Ansem? Well not anymore I guess.
Kingdom Hearts 2:
Wait what do you mean the Organization actually has 13 members? And Ansem's still a problem? Or I guess he's Xehanort now. Wait Maleficent's alive again? Well I guess she's not a huge issue at this point.
Kingdom Hearts 358/2 Days:
The adventures of the Organization during and between the previous games, starring Roxas, the guy who's sort of the protagonist from the previous games, except not! Wow this is fun! Wait, what's going on? [Gradually dissolves into gross sobbing]
Kingdom Hearts Birth by Sleep:
wait so Xehanort's an old evil dude? Hold up what do you mean that he's been behind everything that's happened so far?
Kingdom Hearts ReCoded:
what's going on why are we in a data-world why are we fighting data-roxas whats happening
Kingdom Hearts Dream Drop Distance:
Hang on, Xehanort had carefully manipulated events in order to have everything in all the previous games play out the way they did? WAIT WHY ARE THERE 13 XEHANORTS??