by agreements - an attack against Japan is an attack against the USA.
The general population here in Japan remains peaceful. How much longer will peace will last? As we speak there is a flotilla of 1,000 Chinese fishing boats headed to the disputed islands . If Japan does nothing it will be seen as weak and ineffective . If it reacts it will be accused of nationalism . If the US does nothing to protect it then Japan will see no reason not to ditch the constitution that prevents them from re-arming and strengthening their military.