Seven years after survivng Blue Skull's raid, thirteen-year-old Mavis lives alone on Sirius Island with her friend Zera. Mavis meets Yuri as he searches the island in search of the Sirius Jade, which is the island's cherished relic. Yuri engages Mavis in a game of wits over the ownership of the treasure, but Mavis uses her tactical knowledge and loopholes in the game's rules to beat him. However, their game proves pointless when Precht and Warrod inform them that the jade is already missing. Mavis deduces that Blue Skull possesses the jade, and at her insistence, convinces the begrudging treasure hunters to take her and Zera with them.