Presient Thein Sein visits a thermal-power plant in Kawasaki, Japan

TOKYO—Japanese companies are jostling to line up business in Myanmar, as the country begins a historic push to open its markets and economy to the outside world, after decades of isolation.

Myanmar President Thein Sein, who just ended a five-day visit to Japan, spent much of the time talking to corporate executives. The president stayed two extra days after the regional conference he was attending ended so he could tour a pair of power plants and meet Japanese businessmen who had requested audiences in advance. More…