In the bustling city of Belobog, renowned art thief Sampo Koski undertakes his riskiest mission yet: infiltrating the revered Belobog Museum to steal the legendary Sapphire Sunstone, a priceless gem. Disguised as a charming philanthropist, Sampo befriends Caelus, the unsuspecting son of the museum's owner, in order to weave himself into the inner circle of the family.