Japan's energetic prime minister has apparently decided that the road to Washington lies through Seoul. Yasuhiro Nakasone will precede his Jan. 18 White House meeting with President Reagan with a flying visit to Seoul to see President Chun Doo Hwan early next week.
Although Japanese chiefs of government have visited South Korea before, this is the first working-level summit between Japanese and South Korean leaders. Previous visits were ceremonial occasions. Mr. Nakasone's visit was arranged in secrecy during the past several weeks and announced only Jan. 5.
Japanese relations with South Korea have their own rationale and momentum. But the timing of Mr. Nakasone's visit to Seoul the week before his meeting with President Reagan is regarded by many political observers here as something of a coup.
It will enable Mr. Nakasone to come to Washington with a positive achievement which is a result of his own initiative in foreign affairs. Close, harmonious relations between Japan and South Korea are very much in Washington's interest, for the United States is the security shield of both countries, and uncomfortable or hostile relations between the two only adds to American security problems in East Asia.
Japan is the major Pacific ally of the US. But under Mr. Nakasone's predecessor, Zenko Suzuki, Japanese-American relations turned sour because of trade frictions and American irritation over Japan's grudging defense effort. Mr. Nakasone has made restoration of a better partnership with the US the top foreign policy objective of his administration.
But given the prolonged economic recession in the US and the growing trade gap between Japan and the US (last year, Japan exported nearly $20 billion more to the US than it imported), Mr. Nakasone's best efforts are not going to work wonders overnight.
At least, however, he can try to convince an increasingly skeptical American establishment - especially the Congress - that Japan is a loyal friend and a trustworthy ally, and that when times are difficult, Japan is prepared to take up a fair share of the common responsibility for world economic stability and the defense of the Western nations.
A better political and economic relationship with South Korea will add weight to Mr. Nakasone's presentation. Japan and South Korea have had a generally unhappy recent history, going back to the 35 years Japan ruled Korea as a colony and exacerbated by South Korean resentment that the Japanese do not sufficiently recognize the role their small country plays in safeguarding Japan's own security.
It was South Koreans who died in tens of thousands during the communist North Korean invasion, while it was Japanese who profited by supplying equipment to American and South Korean forces pushing back the invaders.
Even today, the major opposition party, the Japanese Socialist Party, oppose any hint of a Japanese security relationship with South Korea. The opposition regards President Chun and his predecessor Park Chung Hee as fascist despots, at the same time condoning the far more repressive communist dictatorship of Kim Il Sung in North Korea.
The abduction by South Korean agents of opposition leader Kim Dae Jung while he was on a lecture tour of Japan nearly a decade ago made Japanese relations with South Korea even more difficult.
President Chun has since exiled Mr. Kim and his family to the US after successively commuting his death sentence and then giving him a medical discharge from prison. The atmosphere between Japan and South Korea has improved to the point where Mr. Nakasone can take up directly with President Chun - with every chance of success - the vexed question of Japanese economic aid for South Korea.
It is expected that the two leaders will agree on Japanese aid totalling $4 billion for South Korea's current five-year plan, including official development assistance beyond the $1.5 billion limit Tokyo has hitherto been willing to offer.
More important, if Mr.Nakasone succeeds in opening a new era in Japan's relations with South Korea, he will have added an intangible but important dimension to the total security picture in East Asia and to the credibility of the American shield in that region.