First, this was only the view of a single Japanese soldier.
Second, by the time he wrote that paragraph, there had been no enemies invading Japan. So what he described about how Japanese civilians would greet enemy occupiers were purely out of imagination or assumption.
Ironically, when eventually US soldiers occupied Japan, the civilians didn't behave as this soldier described. They did things similar to the people in Hangzhou.
Third, for civilians, nation is only a concept and is not important. Both you and me abandoned the original citizenship and were naturalized as Canadians. Given the chance, a lot more Chinese would do the same. Who cares about the nation!
Lastly, the best wisdom for civilians is not to be hostile to any military powers, no matter it's the army of their own nation or the invader. Both can do great harm to them.