This extra package contains the fanbook and the osts in the game. The fanbook not only contains full resolution images from the game, but also drafts, concepts, and exclusive drawings by the main artist and other artists. You can also see snippets of dialogue between the artist and the writer that made the game the way it is. After downloading the DLC, open the folder for Vision of Aurora Borealis, and you will find them inside a folder named extra_content.