The real test of an NSP installation's integrity comes with the Downloadable Content (DLC). Pirate Warriors 4 had a robust Season Pass, introducing characters like Charlotte Katakuri, Vinsmoke siblings, and the massive Charlotte Linlin (Big Mom).
This is the most common error. If your Base Game is but your DLC NSPs are [EU] , they will not recognize each other. The Title IDs must match. one piece pirate warriors 4 nsp update dlc work
: