After quitting his job at a toxic company, Shiro Amata moves into the house his grandmother left him in her will. There, he soon makes two life-changing discoveries: one, his grandmother was really a witch from another world, and two, said other world is just on the other side of her closet door! Thanks to a book she left for Shiro, he also manages to obtain an all-powerful skill called "Equivalent Exchange," which allows him to turn money from his world into otherworldly currency and vice versa.

With this, Shiro decides to set up shop and sell convenient items like matches to the colorful inhabitants of the other world. His plan: make a massive profit on the goods he brings from home to become so rich that he never needs another job ever again!