In Kagoshima, tonkotsu does not mean a soup. It means bone-in pork simmered down, and it is given about three hundred years of history. The account is that Satsuma warriors made it in the field, at battle sites and hunting grounds, and that Saigo Takamori was fond of it.

The method still reads like outdoor cooking. Bone-in ribs go into oil and are browned. Shochu made from sweet potato is poured over them, the heat is turned up, and the alcohol is driven off. Then water, and about an hour of simmering, before daikon, burdock, and konnyaku join it.

Brown sugar and miso go in at that point, and from there it is a long slow reduction with the scum skimmed off as it rises. The shochu is doing two jobs at once, taking the smell off the pork and putting flavor back into it. In Kagoshima city the daikon that goes in is often Sakurajima daikon, grown on the volcano.

What it was, originally, was food for men sitting in a circle outdoors around one pot, drinking shochu and taking portions out as they went. What it is now is something families make at home with no occasion attached, and something served in school lunches. A dish invented on a battlefield ends up in a child's lunch tray, and nobody involved finds that strange.