That 'law' has been there since WW2 after AMERICA made them a feminist soy state.
this isnt true the law to censor adult content was made in 1907 and WWII started in September 1, 1939 and ended in September 2, 1945
The 1907 Criminal Code’s Article 175 outlawed the distribution and display of “obscene documents,” (including adult content)
Japan was trying to model itself after the West, which was hugely conservative at the time Ironically, there was massive cultural acceptance and demand for pornography at the time but Japan was just trying to adopt western laws during an era of conservatism
later in 1950 they got harder on censorship etc
and if anything USA was a soy country back then with theyer conservatism which japan was trying to adjust to back then
(also WWII didnt have anything really to do with japan at start it was germany ADOLF HITLER who started turning germany into a nazi state killing jews etc if you want to know more just fucking read about it anyways if you already try to put history into a adult game forum atleast get it right)