One Piece’s author, Eiichiro Oda, is known to be a meticulous planner, paying attention to every small detail in the story and planning years ahead. In fact, for certain things, Oda has planned decades in advance and that's what makes him a very special author. Oda is also known to be absolutely incredible at foreshadowing. Using a bit of the story to hint at a much larger future event is where Oda truly shines.