Only 2 parties oppose any form of change in the current constitution of Japan

In the past, the communist party and the socialist party (now called the Social Democratic Party) were two major forces trying to revoke the constitution of Japan. However, as soon as Japan emerged as a major economic power, they have become the strong proponents of the current constitution of Japan. It obviously suggests that the Japanese leftists have been much influenced by such hostile nations as South Korea, North Korea, China, and Russia who vehemently hope that Japan will remain militarily weak.