Lupin III: Twilight Gemini no Himitsu
Genres: Action, Adventure, Comedy
Type: Special, Episodes: 1
Aired: Aug 2, 1996
Source: Unknown
Rating: R+ - Mild Nudity
Synopsis:
A dying mob boss entrusts Lupin with a diamond that supposedly is the key to a vast treasure. But when Lupin is attacked by an assassin and saves a mysterious girl from trouble, it becomes clear that that there's more to this treasure then meets the eye... 

(Source: ANN)