TOKYO — The drizzly weather didn’t dampen the excitement at the annual spring imperial party last month as the royal family strolled along Tokyo’s Akasaka Palace grounds. Mao Asada, the Olympic figure skating silver medalist, was so overwhelmed when Emperor Akihito spoke to her that she managed only to repeatedly reply “yes,” and “thank you very much.” It was a typical reaction that shows the magnetic hold the emperor and empress have over the Japanese people. Missing as usual from the festivities was Crown Princess Masako who suffers from a stress-related disorder that causes anxiety and distress and only occasionally...