Conger eel and Awaji onions, simmered together in a light hotpot stock. That is the whole of the dish, and both halves of it come from within sight of the same water.

The eel comes mainly out of the waters around Nushima, where the seabed is soft mud rather than rock. Because the fish is never scraping its underside against anything hard, the skin on its belly stays thin and soft, and that is what the cooks here are after. The currents from the Naruto strait do the rest, and the flesh comes out firm with real depth to it.

The timing is the other half of the answer. Hamo reaches its season as the Awaji onion harvest comes in, so the two things arrive together without anyone arranging it. The eel is white-fleshed and mild but plump with fat and faintly sweet; the onions are sweet in a different register; the stock holds both.

Hamo is an exceptionally hardy fish and can be transported over distance while still alive. In an era with almost no refrigeration available anywhere, that single biological fact is what allowed Awaji to sell its fish into Osaka and Kyoto at all, and it is the reason the eel remains indispensable at the Gion festival and at the Tenjin festival to this day.