Yamada, who works as an ordinary company employee, goes to visit the family home left behind as an inheritance by his late grandfather, and there he finds a door to another world!! Beyond the door, he meets a talking black cat and a homunculus girl, and as he begins living together with them, he enjoys a cheat magic life in modern Japan and a heartwarming slow life in another world♪

Thirty years have passed since the world and the otherworld known as the Frontier were connected. Countries around the world began exploring the Frontier in search of new resources. Now, if they have the qualifications, even civilians can go through the gate and enter the Frontier. And so, the profession of bringing back resources and selling them, the adventurer, was born. Okita was suddenly fired from his company. With barely any savings, he became an adventurer to make a living. On his first adventure, Okita acquired the skill of alchemy. From that moment on, Okita Hajime's life began to shine with gold. At the same time, the Golden Witch was born, who would break the common sense of the world.