is one piece episode 518 filler?

The episode starts with Fake Luffy threatening Luffy and ordering him to apologize for not only not seeing him but also colliding with him in the street. Luffy remembers the moment when he landed on the Sabaody Archipelago along with the Kuja Pirates.

Hancock tells him that they have to bid goodbye here because she can not let anyone know about their relationship yet and gives him a mustache (disguise) to put on so that no one recognizes him at all. Luffy says he does not need it but takes it anyway.