300 years ago, the demon lord attempted to take over the world but was defeated by a hero. But now, the demon lord has been reincarnated in the form of a cute girl who doesn’t have any memory of her past. She still retains the same deadly powers, but her only resource is the memory robot assistant. The reemergence of the demon lord also means that somewhere, a new hero has appeared. The demon lord sets out and locates this new hero but, the one she finds is Alsha, a timid boy who's weaker than the average human. This is the story of the most powerful demon lord in history and the weakest hero in history.