You can navigate back to 2015 posts on the official dev blog. While some direct MediaFire links from that era may be dead, many remain active.
Communities on platforms like Reddit or Discord maintain "Build Museums" where they host ZIP files of every version ever released, including the popular October and December 2015 builds. Key Versions from 2015 to Watch For Yandere Simulator 2015 Build Download LINK
While the official Yandere Simulator Website typically hosts only the latest version, there are several community-maintained and semi-official ways to download 2015 builds: You can navigate back to 2015 posts on the official dev blog
You can find the original announcement posts and (sometimes still active) Mediafire/Mega links by navigating to the 2015 monthly archives Yandere Simulator Development Blog . Notable 2015 milestones include: April 2015: Key Versions from 2015 to Watch For While
Unlike the modern launcher, 2015 builds are "portable." Simply open the extracted folder and run the YandereSimulator.exe file directly. Compatibility: