The shop generally credited with inventing it, Ajidokoro Kano, opened in 1949. Its founder had previously served tendon, the rice bowl topped with tempura and a soy-based sauce, at a place in Asakusa in Tokyo.

His reasoning has been recorded, and it is admirably simple. If the thing can be done with soy sauce, then it ought to be possible to do it with miso as well. So he took mame-miso, the soybean miso that Nagoya is known for, cooked it down into a thick sauce, and poured that over a freshly fried pork cutlet.

Which means the real ancestry of the dish is not pork at all. It is the tendon sauce, rebuilt out of a different fermented bean, and the cutlet is almost incidental to it. The miso is dissolved with sugar and dashi until it thickens, and because it is mame-miso the result is very dark, with a trace of sourness and bitterness that a lighter miso would not give.

The shop added egg to it because customers asked for egg, and then began serving the cutlet on a separate plate from the rice because customers asked for that as well. The shop did not print a menu at all until the winter of 2004. Before that point, everything in the place was ordered out loud.