An unaired OVA episode of Kore wa Zombie Desu ka? of the Dead. It is the 11th episode and was bundled with the sixth volume of the manga.

A girl named Olga is pursued by both the World Government and a man named Mad Treasure, as she is the only one who knows the location of the Pure Gold, a substance that can buy the entire world. Olga ends up sailing with the Straw Hat Pirates, and they journey to find the Pure Gold on the lost island of Alchemi, which is located inside the stomach of a large angler fish named Bonbori. (Source: IMDb)

This special will have the Straw Hats fight Foxy again in the New World on Nebulandia, an island that nullifies Devil Fruit powers.