One Piece: Strong World is a free volume distributed to the first 1.5 million attendees of the fillm bearing the same name. Icluded is the special prologue chapter. Chapter 0 depicts events 20 years before the current timeline of the manga. 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.