We've received some comments on the "extras" DLC (Downloadable Content)
and that some people couldn't find the files (the soundtrack, artbook images and poster).
The description of the Extras says: "These are the extras - the soundtrack by Iede Saudek and Thomas Krze, the preliminary works by Camila "Bura" Gormaz http://www.bura.cl and a hi-def illustration by Lia Margot. After downloading the DLC, open up Invisible Apartment's folder to find the "extra" directory."
This is done at some other visual novels we've seen.
We recognize that some people couldn't find the files and so we made it our ToDo to link the DLC into the game. We're working on it being possible to access the files from the game. This functionality will be added soon.
If you have any questions than feel free to ask.