Cajoled into revealing how the Lupin gang came together, Daisuke Jigen recalls a time when Lupin III wasn't as well known, Goemon was searching for the ultimate sword, and Zenigata was chasing Fujiko. Jigen himself was a mafia bodyguard and sharpshooter who was sent after Lupin after he attempted to steal his boss's treasure. But there's more to the treasure than expected, especially the protected key to it.