Humans are in desperate need of a trump card. They complete the Reincarnation Spell, hoping to summon mighty warriors from another world to defeat the demons. However, instead of heroes being summoned, the Reincarnation Spell was strong enough to release the seal that trapped the most powerful race in the demonic species—the Nenniaidae. They are unearthly beautiful women with seemingly bottomless amounts of mana. Exclusive to Nenniaidae, these demons possess both male and female sexual organs. Humanity has lucked out in two ways: only a single Nenniaidae was released, and our protagonist controls her body. A body that can be described as the typification of elegance, but with such destructive possibility, she can be dubbed the embodiment of destruction. The latter circumstance is what saves humanity from complete extinction. He, or now she, fights with the humans to take out the Demon Lord and his armies.