From the introduction: Wanted: Dead or Alive. Live for fun, live for the adventure. ... Half the game of One Piece is survival. It requires [you] to keep food charts and survive the harsh seas and the incredibly dangerous waters of the Grand Line. You have a choice in the game: do you become Pirates, Bounty Hunters, or Marines? [Your decision will determine] who you fight for and against in the great world of the sea. User summary: The One Piece game uses several standard "D20" concepts in a blend with homegrown rules intended to support the setting. One Piece: Game Master's Guide (Version 2) differs from One Piece: Game Master's Guide (Version 1) primarily by incorporating almost the entire contents of One Piece: Player's Guide.