Under orders from Headmaster Uther, Eugene forms a party with Sumire, a reincarnator from another world. The pair enter the Last Dungeon in search of her lost memories only to encounter a powerful Boss. However, Eugene finds that Sumire's Ifrit mana is so powerful that even his white mana can't overwrite it. With her help, he can finally fight and deal damage against his enemies. Filled with new hope and eager to pursue his once-abandoned dream of becoming a magic swordsman, he sets off to explore the Last Dungeon with Sumire. But while Eugene chases martial mastery with the sword, Sumire has other goals—such as becoming Eugene's partner even off the battlefield! Between her natural shyness, Eugene's oblivious nature, and the appearance of a rival for his affections, Sumire has her work cut out for her.
