My guess is that the game will check to see what endings you've already completed to open up new paths. It might seem like a completely different story from day 1 once you get the first ending. That's all guesswork, though.I see. But how would you do a purity route if most of the main story lines require you to have practically every character to max? At the end of chapter 1 you're practically in a relationship with everyone except for Maya, Yumi, Rin, Miku, etc.