Set during the late 1960s of the Shōwa era, the film follows gentleman thief Arsène Lupin III and his crew to Paris and Brazil to find the whereabouts of the Bresson Diary, a treasure even Lupin's grandfather Arsène Lupin failed to catch. A battle for the mechanical diary is unleashed as a Nazi treasure-hunter group led by Lambert and Geralt are also in a race to steal it, with the prize that whoever deciphers its mystery will be the owners of an enormous fortune.