Is the new ‘One Piece Fan Letter’ a spin-off canon or filler?

The ‘One Piece Fan Letter’ series, confirmed as canon and originating from ‘Straw Hat Stories’, explores the Straw Hat crew’s daily lives. Though initially thought to be filler, it is an official spin-off recognized by Eiichiro Oda, offering fresh perspectives and enriching the ‘One Piece’ narrative.