Goemon is coerced by Lupin into to winning the confidence of the young woman Chloe Cazal. She was apparently a close friend of the late Belgian millionaire Andre Regnie, who gave her an immensely valuable gem necklace made before the Russian Revolution, which has made Chloe a target for the descendants of its original owners. While looking for her in the town of Sirena (and struggling with the attention of a local Anicon's visitors), Goemon befriends a boy named Jean who lives in Chloe's neighbourhood...