Lupin has invited all of his friends to a villa on a private island. It's the first time they've seen each other for the past five years. Lupin is planning a big surprise while they are all at the villa except Fujiko, Goemon and Jigen find Lupin's behavior to be unusual. They are also curious about who the man in the iron mask is, who is chained up to a wall for the reasons they are about to find out.