If this RAR file contains the August 2020 community update or is a misdated version of the 2017 patch, it likely addresses common technical flaws in the PC port:

: Patches often addressed issues like BGM not returning to normal after events or dialogue initialization errors during a second playthrough. About Princess Maker 3: Fairy Tales Come True

: Early versions of the game suffered from slowdown in fullscreen mode and lacked proper 16:9 optimization. Updates typically aimed to improve compatibility with Windows 7 and above.

Princess Maker 3: Fairy Tales Come True » Patches - SteamDB