Risk estimate is extremely difficult task for people.  People who suffered directly the certain risk tend to overestimate it, on the other hand, people who have no experience of that risk tend to forget it.  Japan belongs to the latter category. Due to its long time lowest crime rate in the world and its mono tribe culture, even after the 9/11 attack in US, most of the people have not considered the terrorist risk in Japan. As political environment is completely different from US, of course probability of attack by the Arabic terrorist group against Japan is extremely low compare to US, but Japan has experience of the Sarin attack in Tokyo by an extreme religious group called “Omu-shinrikyo” in 1994 and several hijackings by the Japan Red-Army in the past.  After the economic boom in 1970’ and 1980’, most of the people become satisfactory with its middle class living standard, as it has been the largest ODA provider to the developing countries, feeling of the developing countries to Japan has been relatively good so far and certainly there has been no reason of attacking against Japan. The terrorism type of risk seems to have disappeared in Japan for a long time.
But environment is gradually changing.  Japan is still in the worst economic slump since 1990 and there is no sign of recovery.  Unemployment rate is raising, crime rate is also raising. ODA has been cut 10 percent and it has become the second ODA provider following US.  North Korean spy vessel fired against the Coast Guard patrol boats in December 2001. These facts show that probability of large scale attacks in and around Japan is increasing day by day, year by year.  
     On the other hand, under the globalized economy, everything is moving beyond the borders as so called “supply chain”. It means that parts of the Weapon of Mass Destruction may be transported through Japan to the other specific country or may have been produced in Japan.
     Definition of “terrorist risk” is extremely difficult task, but if it means the risk which causes large consequence in Japan or elsewhere, I am sure that large terrorist risk already exists in my country.
     I would recommend that experts get together and assess those consequence and probability seriously, make efforts to reduce those probability, and prepare an effective national response plan  utilizing ICS type of emergency management system to remove sectionalism within the government structure in Japan.