Sorceress Lina Inverse and her rival Naga the Serpent sail to Mipross Island chasing rumors of its hot springs, only to find the island gripped by a decades-old grudge. Joyrock, a mazoku who slaughtered the island's elves years earlier and absorbed their power, still lurks nearby, and elderly mage Rowdy Gabriev has hunted him ever since to avenge an elf he loved. Lina and Naga get pulled into the fight as Joyrock stirs back to life. This film is a prequel to the main Slayers TV series.