It is called yakitori and there is no chicken in it. Pork shoulder is cut into bite-sized pieces and threaded onto skewers alternating with wedges of onion, grilled over charcoal, dipped into a jar of sauce, and grilled again. It is eaten with western mustard.

The origin is wartime. In 1937, with the war in China, farmers were pushed to raise pigs to increase the food supply. By 1939 pig farming was being encouraged nationally so that army boots could be made from the hides.

In Muroran the arrangement was that apart from the skin and the meat, what was left could be consumed within the city, and so pork offal turned up in quantity at the stalls.

Onion rather than leek has a similarly practical explanation: Hokkaido grows onions, they were cheaper, and they suited pork. The mustard came off the same shelves as the mustard for oden and tonkatsu. Almost nobody here makes it at home. You buy it from a specialist shop and carry it to wherever people are gathering. Before the war the stalls here had been grilling wild birds, and pork simply undercut them. Everything about the dish changed to fit what was available. Only the name stayed chicken.