is one piece episode 380 filler?

About 50 years ago, the Rumbar Pirates left the young Laboon in the care of Crocus at the outlet of Reverse Mountain. Brook, then the crew's musician, promised the whale that they would sail around the world, and return for him.

Some time later, the wreckage of Brook's ship floats aimlessly in the Florian Triangle. Brook, resurrected by his Yomi Yomi no Mi Devil Fruit powers but not before his body decayed into a skeleton, is gathering the remains of the rest of his crew.

The last skeleton he stores below deck is that of Mizuta Madaisuki. He places the skulls all in a separate casket.