Washington — Now comes the hard part. Given the amenities required for a first meeting, and the participation of other officials, President Reagan and Japanese Prime Minister Yasuhiro Nakasone had only a limited amount of time to do real business at their meeting on Tuesday. An unscheduled breakfast meeting between the two leaders was added for Wednesday morning.
But the hard part - the real test - will begin once the White House meetings have been completed.
The first meeting has clearly enhanced mutual confidence between Reagan and the new Japanese leader. But it seems clear that there are no easy answers to US-Japanese differences. The only solution is likely to be protracted negotiation, some of which will begin when Secretary of State George Shultz visits Japan at the end of this month.
According to a Japanese spokesman, Taizo Watanabe, Mr. Nakasone wants to strengthen relations between Japan and the United States. But Mr. Watanabe said if Americans continue to criticize Japan because of its trade practices, it may simply strengthen the hand of the opposition parties in Japan and make it more difficult for Nakasone to revise trade procedures.
Watanabe said that Nakasone wants to reaffirm Japan's security alliance with the US despite the furor that his predecessor, Zenko Suzuki, created in Japan by using the word alliance. The word is sensitive because of strong pacifist sentiment in Japan and because opposition parties in the Diet, or parliament, oppose any strengthening of the US-Japan defense relationship.
Watanabe said that Nakasone expects a ''rather rough and tough session'' in the Diet as a result of Nakasone's use of the word alliance during his visit here.