An unexpected encounter with a trio of bandits reunites the skilled sorceress Lina Inverse with Naga, a fellow magic user who views herself as Lina's rival. Using a plundered discount coupon, the food-loving pair head to Mipross, an island known for its hot springs but wrapped in mystery. While Lina tries to enjoy her stay, she desperately attempts to ignore the strange dreams that have been haunting her for some time, particularly since arriving on the island. With her relaxation at risk, Lina is pulled into a request from the king alongside Naga, resulting in an incident that will forever alter the fate of the Island of Promise.