NSP files are encrypted Nintendo Switch game packages. Downloading them from unauthorized websites without a license is illegal (copyright infringement) and carries risks:

Unauthorized NSP files can be bundled with malware , spyware, or viruses that can corrupt your system or steal personal data .

: You can unlock all DLC for Mega Man 9 and 10 by entering a secret code at the title screen: Up, Down, Left, Right, Left, Right, Down, Up, Up, Down

: Pirated versions cannot connect to official servers for leaderboards or multiplayer.