The original film told the story of an Italian World War I fighter pilot who was transformed into a pig by a magical curse. The English language release featured Michael Keaton in the titular role.
Miyazaki is quoted as saying that The Last Sortie will be set during the Spanish Civil War and that it will represent a sort of artistic escape for him at the moment, focusing on a male character after so many films with female protagonists.
A sequel to Porco Rosso would represent the first direct sequel on the part of Miyazaki’s Studio Ghibli. Previously, characters have crossed over between films (as was the case with Whisper of the Heart and The Cat Returns as well as the Susuwatari creatures in both My Neighbor Totoro and Spirited Away.