Many file-hosting services have upload limits (e.g., 5GB per file). Uploaders split the game so it fits these constraints.
The existence of a "Part 06" usually points to one of two scenarios: Nioh.Complete.Edition.part06.rar
If you successfully reassemble all parts, you gain access to a "Souls-like" masterpiece developed by Team Ninja. The Complete Edition includes: Many file-hosting services have upload limits (e