Not really a point. I guess because security demand is generally low, it was easy for the assassin. But compare the number of 'everyday crime' like theft, murders and gunfights to the US and I guess you easily come to the conclusion that Japan is safe.

It could be that a dedicated lunatic was able to get a top level politician with a DIY 17th century grade musket exactly because anticipation of such an event at politician public appearance in Japan is lower than on a regular day in US elementary school.