Three conditions. A soy sauce tare. A layer of lard sealing the surface. Raw onion, chopped fine, on top. Meet all three and you have a Hachioji ramen. Miss any one of them and what you have is a different bowl with a different name.

The onion came from a holiday. The founder of the original shop encountered a bowl in Hokkaido with chopped onion in it, liked the texture, and tried to reproduce it at home in western Tokyo. The problem was that raw onion is sharp, and the sharpness would not go away. The bowl came out with a hard edge on it.

His fix was lard. Adding pork fat to the soup suppressed the bite and brought the sweetness of the onion forward instead. So one of the three defining features exists as a solution to a problem created by another one of them, which is the kind of thing that usually gets tidied out of an origin story.

The fat has a second effect nobody planned. It caps the surface and the heat cannot escape, so the bowl stays scalding much longer than it should. In 2003 city staff, a university lecturer, and a group of students formed an association around all of this and wrote the three rules down where anyone could read them.