From the introduction:
Princess: The Hopeful is a game about the promises of our youth fulfilled, inspired by the “maho shoujo” or “magical girl” genre of Japanese anime and manga. Princes and Princesses are those who haven’t given in to that fear of inadequacy and failure. They come from a world unlike the World of Darkness, a better world, a kinder world, a just world. They come from the world we all wished we could make before we knew it was impossible – and they seek to prove us wrong. A better world wasn’t impossible, and it still isn’t. As a Princess, power isn’t a gift to you, it’s a responsibility.
The first "edition" of the game was more-or-less intended as a standalone implementation within The World of Darkness. After the release of The God-Machine Chronicle the game received a complete overhaul, including supporting materials.