One Piece's Undersea Prison Advancement was an important plot in the One Piece series, which described Luffy and the others 'experiences in the Undersea Prison. The story takes place in a fictional world. Luffy is invited by Vice Admiral Noah to join One Piece Island in order to find a way to become the king of pirates. As they advanced into the city, Luffy met many interesting characters, including Warden Kalibu and his men. Luffy encountered many difficulties in the city, not only facing the criminals in the prison, but also engaging in a fierce battle with Kalibu. In the end, Luffy successfully escaped from the city and went to the New World to find a bigger adventure.