One Piece 3D2Y: Overcome Ace’s Death! Luffy’s Vow to his Friends(2014)

ONE PIECE "3D2Y": Ace no shi wo Koete! Luffy Nakama to no Chikai

This new TV special tells the two years of Luffy's training with Silvers Rayleigh in Rusukaina Island after the Battle of Marineford, which has never been told in the manga or TV anime. It also features a new villain named Burndy World who is known as "The Destroyer of the World" and has the power of the MoaMoa Fruit (its ability is still unknown). Luffy has to protect Boa Hancock from the new enemy who escaped from the level 6 of Impel Down. He is newly designed by the original creator of the manga, Eiichiro Oda.

(Source: Crunchyroll)