Tatsuya Yamada, a modest middle manager, toils away at his daily work. Then one day, the grandfather who had always cherished him passed away, and he inherited his house according to his will. Having moved into his late grandfather’s home, he decided to enter the off-limits room he had always been warned against. To his amazement, that room led to a house in a settlement in another world, where a little girl awaited him. Learning from the girl that his grandfather was revered as a legendary grand sorcerer, he decided to carry on his legacy and live as a magician in the modern world. As he’s studying magic with the girl and her black cat familiar, he continues his usual grind as a corporate drone, until the unexpected happens—the village chief from the other world asks him to become his successor. Yamada, just an assistant manager in a small-to-medium enterprise, dreams of developing the village and living a laid-back life in another world, yet with neither the funds nor the time. Just then, he discovers the demon-hunting industry his grandfather was part of, and realizing the fortune that could be made, he embarks on a journey to turn his life around. This is the tale of a middle aged archmage, the mightiest of his kind, striving for a leisurely life in a village of another world, vanquishing the demons that lurk in today’s society, and changing his life around.