Friendship is perhaps the most central theme in the entire One Piece series. This can be seen with the main cast since Luffy is without a doubt considered to be the main character, with the whole story revolving around him and his exploits across the sea. However, as important as he is, he would never have made it close to as far as he did had it not been for his crew, who all come together to fill in any gaps that Luffy lacks.