In 1919 League of Nation, Japan “Racial Equality Proposal” and ends in colonialism but USA blocked it.
After WW2, USA violated Geneva/Hague convention and ILLEGALLY interfered with Japanese constitution which even German was NOT victim of.. Literally, even police was not allowed to carry a weapon. Also allies were made immune from prosecution and koreans were added probably to used as a henchmen. Rampant crimes occurred as well as South korea invaded Takeshima island and killed few fishermen. Because of this and Korean war/cold war interpretation became slightly loose and police were allowed to carry weapon as well as self defense force was allowed. Some estimate Allies raped 2 million rapes in Germany, 1-2 million in Japan, and France after D-day. It is easy to believe since Center for Disease Control estimates over 1.3 million rapes per year in USA today.
USA also brainwashed Japan and controlled media, education and false propaganda that vilified japan. Even after the occupation, it remained and Japan had somewhat anti-japan media/education system which are influenced by china/korean spies. Because of this most Japanese naively believe that not having military makes things safe and don’t see imminent danger from china’s aggression.