is one piece episode 988 filler?

Although Luffy attempts to follow the plan, Kid and Killer continue to wreak havoc on enemy units. Meanwhile, at the eastern mountain path, Kin'emon's forces split into two groups.

One group enters the castle while the other continues down the path. Chopper's tank joins the group entering the castle.

Most of them see Big Mom's shadow from the window and dive into the water, but she opens the window to find Chopper's tank. The Big Mom Pirates, led by Perospero, finally make it back up the waterfall and into the country.