The story revolves around a boy named Tasuku Kotone, a student who by chance meets a ghost in a park. The name of this ghost is Keisuke Shinonome, and it is the ghost of a man who used to be a doctor. Tasuku finds out that the ghost has a vast knowledge of medical terms and anatomy, and he can ask for advice for his schoolwork and be guided through their experiences.

At his death, the great sage used the new magic he developed to reincarnate into the future. However, he was deemed to be talentless and abandoned in the forest of monsters where he was picked up and raised by goblins. To repay them, he helped them evolve and taught them magic. The story of the abandoned child who will build what would be known as the great empire of monsters.