TOKYO, SEPT. 7 -- In an atmosphere of warm smiles and congenial commentary, Soviet Foreign Minister Eduard Shevardnadze today completed a historic Tokyo visit that may turn out to be, as Japanese Prime Minister Toshiki Kaifu said, "a turning point in Soviet-Japanese relations."

In sharp contrast to Shevardnadze's last stop here four years ago, when frosty feelings were evident on both sides, this week's trip was full of indications that Japan and the Soviet Union are trying to move beyond a state of mutual distrust that dates back to the Russo-Japanese war of 1904.

Commenting today on the changes in international relations since his 1986 visit, Shevardnadze told a news conference that "the {bilateral} situation has changed, and radically so. We are now poised for discovering new principles that can underlie the relationship in the future."

Among other things, Shevardnadze this week firmed up plans for a visit here next April by Soviet President Mikhail Gorbachev, the man known here as "President Go." "Go" is the first syllable of the Japanese pronunciation of Gorbachev's name.

Gorbachev won a spot in Japanese hearts earlier this summer when he said he would love to visit Japan during "cherry blossom time" -- the spring weeks when Japan's signature flower is in bloom. A visit in late April would bring Gorbachev to Tokyo at prime time for blossom viewing.

At least as important were some vague comments that Shevardnadze offered on a key point of contention between the two Asian powers -- control of four small islands off the northern Japanese island of Hokkaido. Moscow seized the four islands from Japanese control at the end of World War II.

For years now, whenever Japan broached the issue of these "Northern Territories," Moscow insisted that there was nothing to discuss. "Japan should face the reality of World War II," Shevardnadze said in 1986. "The islands are Russian."

This week, though, the Soviet diplomat seemed to concede in the veiled language of international diplomacy that there may be some room for discussion about the islands. Shevardnadze said the northern territories constitute "a very complex and difficult issue." Japanese diplomats and media jumped on that wording, seeing a major step forward merely in Moscow's willingness to concede that the islands amount to an issue.

It has been widely speculated here that the Soviet Union's acute need for financial aid, and Japan's obvious ability to provide it, might offer a modus operandi for solving the territorial dispute.

Japan could provide financial aid as an incentive for the Soviet Union to return the islands -- or some of them, at least -- to Japanese control.

Shevardnadze delicately denied this week that there is any such "linkage" between economic concerns and the status of the islands.

But he seemed to be referring to the island question today when he said that after the two countries develop "a full economic relationship," there will be "a more propitious situation for resolving more complex and difficult issues."

Shevardnadze and his Japanese counterpart, Foreign Minister Taro Nakayama, issued a joint communique condemning Iraq's Aug. 2 invasion of Kuwait. It was a routine diplomatic document -- except for the fact that it was the first time the Soviet Union and Japan have issued a joint statement on an international question.

At his press conference, Shevardnadze also expressed displeasure with the Soviet Union's longtime ally, North Korea. Discussing recent moves toward better relations between the the Soviet Union and South Korea, the foreign minister said his country has a "sovereign right" to talk to officials in Seoul, and complained about North Korea's efforts to "limit our scope of action."