Lupin, the master thief/spy/Jack of all Trades, has been executed, but he is still alive, and not even Lupin himself knows how that is possible. While trying to figure out, however, he and his gang are thrust into a conspiracy involving clones, Lupin's un-trustworthy rival Fujiko, and a miniature madman's plot to take over the world.

(Source: ANN)

Long ago, magic was abundant and enriched the lives of all people until its usage in war. To end the chaos, seven of the most powerful mages gave up their lives in order to seal all magic. Now, almost one thousand years later, their magic seal Magiaconatus hosts Granbelm, a monthly series of battles meant to determine who among its participants is worthy of the title of Princeps, the one true mage. On the night of a full moon, high school student Mangetsu Kohinata is suddenly transported to an illusionary world where six mages are participating in Granbelm. Mistaken for an enemy mage, Mangetsu is attacked by two mages until she is rescued by Shingetsu Ernesta Fukami and her Armanox Viola Katze. However, when Shingetsu is ambushed for protecting her, Magiaconatus grants Mangetsu the Armanox White Lily, allowing her to fight off Shingetsu's assailant. Overwhelmed by the revelations presented to her, Mangetsu decides to help her new friend fight in Granbelm and make her wish come true. [Written by MAL Rewrite]

On the ocean floor, Lupin is once again seeking a treasure hoping to get on Fujiko's good side. As Zenigata chases them on sea and land, people around the gang begin to vanish mysteriously. The fog rolls in and Mamo Kyosuke appears in a burst of light; he claims to be from the future and seeks revenge on Lupin III for what Lupin XIII has done to him. Mamo hurls Lupin, Jigen, Goemon, and Zenigata 500 years into the past; as two warring factions fight over a legendary shrine dedicated to time travel, Lupin must find a way to survive the past to ensure his future.

(Source: Lupin III Encyclopedia)

This movie is a remake of episode 13 in the original Lupin III series.

Woonan is the legendary Great Gold Pirate, earning the nickname after accumulating about 1/3 of the gold available in the world. Even after his disappearance, the tales of his gold being stashed away in a remote island continue to persist, a juicy target that other pirates lust for.

One of the pirates going to great lengths to attain the treasure is El Drago. He and his crew have hunted down Woonan's former crew members one by one, and along the way, they find the map that will take them to the hidden island.

The map is not all they come across; they also manage to come into contact with the straw hat pirates. After a short battle, Luffy and company are robbed and separated from one another. Now they must find a way to make it to the island before El Drago does and take the legendary treasure for themselves.