I recently found the pixiv of the original artist (back then it wasn't still indexed on Google seemingly) and the above version I posted is actually incomplete, as some files are missing. The complete version can be found here:
https://www.pixiv.net/en/artworks/75901449
Additionally, the actual ending is here:
https://www.pixiv.net/en/artworks/75901514
Seemingly, the artist made an improved version of
this one.