Impel Down

The thirteenth season of the One Piece anime series, titled "Impel Down" (インペルダウン, Inperu Daun), was produced by Toei Animation and directed by Hiroaki Miyamoto based on Eiichiro Oda's manga. It deals with the imprisonment of Monkey D. Luffy's adoptive older brother Portgas D. Ace and Luffy's attempt with Boa Hancock's help to infiltrate the great prison Impel Down to save him. Luffy meets several old enemies prisoners from his past in this arc, including Buggy the Clown, Mr. 2 (Bon Clay), and Mr. 3.

There is also a 4 episode arc set outside the current continuity titled "A Gold Lion's Ambition" (金獅子の野望 Kinjishi no Yabō), which serves as a prologue to the concurrently released One Piece Film: Strong World. This arc features Luffy and his crew's run-in with a group of pirates hired by Shiki, the film's main antagonist. Following this arc, the Impel Down story line continues where it had left off. The season began broadcasting on Fuji Television on October 18, 2009, and ended on June 20, 2010, totaling 35 episodes.