The powerful teenage sorceress Lina Inverse and her traveling companion and self-styled archrival Naga the Serpent, having been reunited after Naga was (once again) hired against Lina, obtain two discounted tickets for a tour to the fabled hot springs of Mipross Island. However, they discover almost immediately that those hot springs are fake and the island is controlled by a group of bandits. The two heroines clean up the island from them but learn they have been sent by someone called "the Great Master".