Political extremism in Japan means that there are some people who hold very different or extreme political views than most other people in Japan. This can include things like wanting to change the government in a radical way or committing political violence to get their way.
One example of political extremism in Japan is the group Aum Shinrikyo, which committed a terrible terrorist attack in Tokyo in 1995 by releasing sarin gas in a subway station. The group believed in a mixture of Buddhist and Hindu beliefs and had an apocalyptic vision of the world.
But political extremism can also come in more subtle forms. Some Japanese people believe that the country should return to its traditional ways and become less influenced by Western culture. Others believe that Japan needs to increase its military power and assert itself more strongly in international affairs.
These different views can sometimes lead to clashes with more moderate or mainstream political groups. However, it's important that everyone can express their opinions peacefully and without resorting to violence.