TOKYO — EXCEPT for a brief shudder by the Japanese stock market, the new diplomatic chill felt by Western capitals after the ouster of Mikhail Gorbachev is raising barely a shiver in Tokyo.Relations between Japan and the Soviet Union were already chilly under Mr. Gorbachev, who failed during his six years in power to thaw out the cold war with Japan like he did with Europe and the United States. Even when Gorbachev appeared most threatened by rightists in recent months, Japan was the most eager among its fellow industrialized nations to stiff-arm his request for economic help, citing the need to settle a territorial dispute first. And unlike most Western leaders, none of Japan's recent prime ministers ever developed the kind of close relationship with the reformist Soviet president that might have raised feelings of anger over his removal. Now that Western countries are moving to suspend aid to Moscow after Gorbachev's ouster, Japan finds itself with little leverage in possibly withholding aid or credit. Rather, says Foreign Ministry spokesman Taizo Watanabe, Japan's influence lies in what economic help it can offer Moscow in the future. "The situation unfolding before our eyes would not allow us to proceed with whatever we are planning in the field of assistance," he says. Japan's No. 1 worry, in fact, is that it not be excluded from the hurried talks among Western leaders over how to react to the tense situation in Moscow. Japanese Foreign Ministry officials were hasty to make sure that Prime Minister Toshiki Kaifu held telephone conversations with the leaders of Canada, the United States, and Britain. And as its Western partners prepared to consult each other through the European Community and NATO, Japan reminded them that the best forum for a coordinated policy against Moscow was the Group of Seven club of industrialized nations, which met with Gorbachev at its London summit in July. "We are not under any pressure to do anything," says Mr. Watanabe. As a reflection of its business as usual response, Japan chose not to describe Gorbachev's ouster as a "coup," referring to the events in Moscow as "likely" to be unconstitutional. Japanese officials said they want more information on what is happening inside the Soviet military and in the countryside before making definitive judgments. They are more concerned that economic reforms begun under Gorbachev continue rather than ponder whether the new Soviet leadership is legal. Even though Japan was the one industrialized country that gained the least from Gorbachev's foreign policy, it does hold an emotional stake in at least one bilateral program now under way: visits by private Japanese to gravesites of relatives who died in Soviet captivity during and just after World War II. Officials are reluctant to jeopardize this new access with the Soviets and risk upsetting hundreds of Japanese citizens keenly interested in honoring their dead relatives. "The best response for Japan is not to make hasty decisions," says Ivan Tselichtchev, a leading Soviet scholar on Japan and a visiting fellow at the Japan Center for Economic Research. "Much depends on how Japan assesses events in the Soviet Union," he said, "and then it may follow the US line. I believe that Japanese assistance will not be very positive." The drag on Soviet-Japanese ties has been Tokyo's claim over four northern islands taken by the Red Army in 1945. Gorbachev, on a trip to Japan in April, did not budge on the Soviet claim to the small islands, despite potential massive aid from Japan. With right-wing leaders now taking over in Moscow, Japanese analysts say there is little hope of any progress soon on the territorial issue. "Forget about the islands," says Hiroyuki Kishino, researcher at the International Institute for Global Peace. "The conservatives are opposed to any territorial concessions. Any talks will be more difficult. But Mr. Kishino sees little likelihood that the new Soviet leaders can afford to further beef up the military and revive the cold war. "Even under a conservative leadership, Moscow does not have enough money to improve the military." He adds that US plans to withdraw about 15 percent of its forces in Asia, mainly in Japan and South Korea, could be stalled depending on how Washington perceives the new Soviet leaders. The one sure victim in Japan-Soviet ties is Japanese investment. Already wary of political uncertainty in Moscow, Japanese business is sure to put off plans for anything but small-scale projects in the Soviet Union. "Business was cautious before," says Mr. Tselichtchev, "I can predict that Japanese investors will not be interested now."