TOKYO — As the leader of the free world, and a man never shy around the spotlight, President Trump is rarely a spectator to the events surrounding him. Leave it to a bunch of sumo wrestlers to steal his thunder.

On Sunday, inside the Ryogoku Kokugikan, a stadium near the Sumida River in Tokyo, Prime Minister Shinzo Abe introduced Mr. Trump to Japan’s national sport. It was the last day of an annual grand tournament, and most of the 11,000 fans in attendance sat on mats and cheered the loinclothed wrestlers as they barreled into each other with forces that seemed to defy physics.