is one piece episode 594 filler?

The episode begins with Law explaining his proposal of an alliance to Luffy and Nami. Law reveals he has found a way to take down one of the Four Emperors but Nami disagrees with the idea of forming an alliance and tries to convince Luffy not to agree.

However, Luffy asks Law which one of the Four Emperors he is talking about and after hearing his answer he agrees to his proposal, leaving Nami shocked.