The white mage Lily, who was deemed unfit for the party she had formed with her childhood friends, receives notice of her dismissal. On what was supposed to be her last adventure with the group, they encounter a powerful foe, and Lily is left behind as bait. Barely managing to escape, she falls into a bottomless abyss—only to emerge three years later. Having transformed into the mysterious and advanced class known as the "Holy Witch," Lily begins her journey back to the surface from the deepest levels of the dungeon. Thus begins her tale of reverse dungeon conquest, starting from the highest difficulty—let the adventure commence!