Also, I asked a question earlier about not seeing the part2.rar file for the newest build of Shiro no Yakata posted by Noble Kind, in the comments. Well, after looking through the comments, it turns out that the folder that first pops up when you unzip the part2 zipped folder is actually a .rar file! It doesn't look like one the way the first part does, and hovering over it does not reveal the .rar ending that should be there (in fact, it looks exactly like a zipped folder, and unzipping that folder/file again was what lead to the problems for me in the first place). I only noticed because I thought there was something wrong with my native unzipper, so I unzipped it online, and that's when I saw that it was a .rar file.
After that, follow the instructions (put both the part2.rar file and the part1.whatever file in the same folder, then run the part1.whatever file) and you should be good to go! Leaving this here in case anyone else had the same issue I had.