Lupin III: Chi no Kokuin - Eien no Mermaid
Genres: Action, Adventure, Comedy
Type: Special, Episodes: 1
Aired: Dec 2, 2011
Studio: Telecom Animation Film
Source: Unknown
Rating: PG-13 - Teens 13 or older
Synopsis:
Two jewels are the key to the ancient treasure of Yaobikuni. But legend has it that the only person who can find the treasure is one who can walk the path of death.

And why is Lupin interested? This is the one treasure his grandfather sought but did not steal.

(Source: AniDB)