Prime Minister Naoto Kan is finding his nation dependent on the US in responding to North Korea, even as public opposition to the US base on Okinawa remains high.
The speed with which the fishing boat dispute turned ugly suggests how little has been achieved in China-Japan reconciliation over the past five years, say analysts.
The confrontation in disputed waters between a Chinese fishing boat and Japanese Coast Guard vessels have quickly soured China-Japan relations. Neither governments appear ready to lose face in the standoff.
Japanese Prime Minister Yukio Hatoyama said Wednesday he would resign after coming under fire for weak leadership and reneging on a promise to move a US military base off Okinawa island.
Exit polls on Sunday gave the Democratic Party of Japan (DPJ) more than 300 seats in Japan's 480-seat Diet (parliament), ending more than 54 years of nearly unbroken rule by the Liberal Democratic Party.