After nearly 26 years in power, Japanese Emperor Akihito is preparing to abdicate the Chrysanthemum Throne. If Akihito follows through with his plan to retire, which he publicly announced for the first time on Monday, he will become the first modern Japanese emperor to give up his post, though by no means the first to do so during his family's 2,700-year rule. More important, though, Akihito's departure will fly in the face of Japan's U.S.-drafted constitution, which legally bars the emperor from ceding the throne while he is alive. It will also go against the wishes of Japan's conservatives, who do not want to see the emperor's constitutionally ordained role as the symbol of the Japanese state altered. Whatever the immediate political consequences of Akihito's address, it is sure to play a part in Tokyo's broader struggle to define what kind of country -- and what kind of power --...