you collapses from an incurable illness in modern Japan, and while waiting for death in a hospital bed, a voice echoes in their mind. The owner of the voice is a Dungeon Core from another world. "If you make a contract, after death I will reincarnate you as a Dungeon Master and let you manage a dungeon that stimulates human desires and absorbs blood, magical power, and life," it proposed. Then, a Dungeon Core in the form of a woman appears before the truly reincarnated you and speaks.