Some years ago I was sitting at the counter of a rather exclusive sushi restaurant in the Roppongi district of Tokyo when I noticed that a middle-age man a few stools along was making monosyllabic comments each time I ordered a morsel of sushi or slipped one into my mouth.

"Wow," he said as I chewed my yellowtail; "amazing" when I swallowed my sea urchin.

I rose to the occasion, ordering expensive slivers of raw fish, while showing off my hard-earned prowess at the sushi counter. When I asked for the bill it was 24,000 yen, a veritable fortune for me, and I realized that I had violated the cardinal rule of Japanese cuisine: Do not try to impress people in a sushi restaurant.