ONE PIECE: STRONG WORLD

One Piece Strong World 0 is a one-shot story published in Weekly Shounen Jump as a special prologue chapter to the 10th One Piece movie, Strong World. This one-shot depicts events 20 years before the current timeline of the manga, One Piece. The main focus is the relationship between Shiki, the Golden Lion and Roger, the Pirate King. In addition, it shows what other characters were doing 20 years ago.
(Source: MAL Rewrite)