The guy goes by the nickname of "rurubell". He developed this VN over the span of ~4 years, actively discussing the development on 2ch imageboard. Then, struck by events in personal life, rurubell slowly disappeared from the Internet, leaving all the source files free to download.
I decided to make a tribute page on my website, so a few random people who will visit could discover this visual novel. This page will serve as a mirror for all the source files I could gather. I will also leave the links to all websites/archives connected to this VN.
The author released all the VN's content to the public, though many links are already broken. Below are all the files and links I could find and save.
Links to original threads on 2ch, archived at arhivach:
(Be aware that arhivach changes its top-level domain once in a while)
Thread 1
Thread 2
Links to anivisual - Ukrainian website about VNs, now closed and functioning as an archive:
Project page
VN page
Link to rurubell's GitHub where he published all of the VN's plot and ideas:
rurubell's GitHub page
And finally, direct downloads of source files from my website:
Folder (to open in browser)
Ren'Py Project (contains OSTs also made by author btw)
Backgrounds and their sources
Finished Backgrounds
CGs
Sprites
Copy of VN's plot from rurubell's GitHub
I do not have the built .exe version of Pre-Demo, but you can just download Ren'Py and import the project there.
Here are some screenshots and images from the author that I like: