AT the edge of the balcony, a tiny woman was screaming. The elderly couple in the next row were jumping up and down. Below us, all around the ring at the Kokugikan, Japan’s national sumo stadium in Tokyo, a roaring crowd hurled seat cushions into the air. My husband and I looked at each other in amazement. After two weeks of travel among the intently well-behaved, rigorously unflappable Japanese, were we about to have a peek behind that decorous facade?