You can find the legitimate, DRM-free, and fully updated version of the game on Steam or the PlayStation Store.
Open the first file ( part1.rar ) with a program like WinRAR or 7-Zip , and it will automatically pull data from the other parts to recreate the full installer. Yakuza.4.Remastered-CODEX.part2.rar
If you are looking for your progress, the PC save files are typically located in [Steam Install]/userdata/[YourID]/1105500/remote/ , as noted on SteamDB . You can find the legitimate, DRM-free, and fully