I am busy playing it. I am planning on doing the True Ending. I looked up walkthroughs for each ending and I saw what is called 'Normal Ending'. It something called "Cession" what does this mean? Is it a bad ending?And that is the hardest question to answer! I played them in their order of development. Heck, I'm playing 4 right now as we speak. But to answer that question, it depends whether you want to follow the timeline or not.
However, I will tell you this: If you started with the first game, play the Sideboob Stories after it IMMEDIATELY.