FOR Japan, which abhors a vacuum almost as much as nature does, a rush of sudden change in the world has opened up political voids a bit too empty for comfort.On its northern flank, Japan sees a crumbling Soviet Union, with its military likely in retreat. On its southern flank, Japan watches warily as the United States military leaves its most strategic bases in Asia, Subic and Clark in the Philippines. The result: the cold-war certainties of the past 45 years that allowed Japan to prosper are becoming hollow. Japanese leaders are more than a little befuddled on how to react. On Aug. 19, for instance, when the West was denouncing the coup attempt against Mikhail Gorbachev, Japan was shocked into an awkward cautiousness and insisted, for some unexplained reason, that the action in Moscow was not actually a coup. Then, when Russia sent a top official to Tokyo in a new post-coup openhandedness and offered to compromise on a territorial dispute in exchange for aid, Japanese leaders could only balk, deferring as in the past to Washington on how to handle the Soviet Union. It put off officially recognizing the Baltics until after its Western partners did, and even after Moscow gave its blessing to the Baltics' freedom. And as the Philippine Senate was rejecting a new bases treaty with the US, Japan was mum on the matter, uncertain whether a military vacuum might open up and renew fears in Southeast Asia over the future role of the Japanese military. As a wealthier Japan tries to become more independent of the United States, it gropes for its own initiatives. "We call upon the wisdom of the people of Japan to decide upon an appropriate course for our nation," stated a recent plea from a newly formed group of ex-diplomats and other prominent Japanese. Japan is in need of "crisis management," business leaders argue, that would override a cultural habit of slow consensus-making that has failed Japan at a time of rapid global changes. Japanese business has a strong incentive to make such a call. Dependent on the US market and a US perception that Japan is slowly becoming more Westernized, the top companies fear American resentment toward Japan might be growing, especially after Japan dithered in its support of the Gulf-war effort - giving money reluctantly, late, and at a level below US expectations. And with the 50th anniversary of the Dec. 7 bombing of Pearl Harbor coming up, Japan is in a rush to prevent any more dangerous gaps opening up in its relations with the US. "Given the tensions that exist between our two countries, I cannot dismiss the possibility that the 50th anniversary will make them worse," said US Rep. Stephen Solarz (D) of New York on a trip to Tokyo in early September. Taking the brunt of charges that Japan has feeble leadership is Toshiki Kaifu, who was selected as a caretaker prime minister two years ago and is due to end his term Oct. 30. His political rivals insist that Japan can no longer afford meek leaders. "There has been no other period in which Japan needs to exercise strong leadership [in world affairs] as much as now," said Kiichi Miyazawa, the one Liberal Democratic Party (LDP) candidate who speaks fluent English. But Mr. Kaifu's detractors within the ruling LDP are not clear on how Japan should act in the post-cold-war world. "I have yet to hear a clear, systematic, and logical explanation of what they think Japan should do with international society," says a leading LDP figure, Ichiro Ozawa. He seems to be concerned that Japan not fill a political vacuum with hot air.